WO2011004990A1 - Photodetector capable of detecting long wavelength radiation - Google Patents

Abstract

A photodetector capable of detecting long wavelength radiation, comprising a source disposed on a proximal end of an insulation layer; a drain disposed on a distal end of the insulation layer; at least one nano-assembly coupling the source and the drain between the proximal and distal ends; and at least two surface plasmon waveguides positioned between the source and the drain and juxtaposed to the at least one nano-assembly in a longitudinal direction of the at least one nano-assembly, wherein one of the at least two surface plasmon waveguides is positioned along a first side of the at least one nano-assembly, and another of the at least two surface plasmon waveguides is positioned along a second side of the at least one nano-assembly that is opposite the first side.

Description

PHOTODETECTOR CAPABLE OF DETECTING LONG WAVELENGTH RADIATION

The prsent invention relates to apparatuses capable of and techniques for detecting long wavelength radiation.

Detection of long wavelength radiation at room-temperature has several useful applications, including military and civil uses. For example, photodetectors for detecting long wavelength radiation can be used in medical equipment, as seekers in missiles, in narcotics control, etc. As nano-technology involving the design of nano-scale electronics including optical devices and photodetectors (i.e., structures having a size of about 100 nm or smaller) continues to develop, it is envisioned that advances in nano-technology may be applied to the design of such nano-scale electronics (i.e., optical devices and photodetectors) for improved efficiency and detection.

<SUMMARY>

Apparatuses capable of and techniques for detecting long wavelength radiation (e.g., infrared spectrum light) are provided. In one embodiment, a photodetector capable of detecting long wavelength radiation includes a source disposed on a proximal end, a drain disposed on a distal end, at least one nano-assembly coupling the source and the drain between the proximal and distal ends, at least two surface plasmon waveguides positioned between the source and the drain and juxtaposed to the at least one nano-assembly in a longitudinal direction of the at least one nano-assembly, and wherein one of the at least two surface plasmon waveguides is positioned along a first side of the at least one nano-assembly, and another of the at least two surface plasmon waveguides is positioned along a second side of the at least one nano-assembly that is opposite the first side.

In another embodiment, the photodetector may further include a transparent gate positioned in proximity to the at least one nano-assembly and the at least two surface plasmon waveguides and further being arranged so as to extend substantially parallel to at least one of the source and drain.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

FIG. 1 shows a perspective view of an illustrative embodiment of a photodetector.

FIG. 2 shows the spectrum of long wavelength radiation that may be detected in an illustrative embodiment.

FIG. 3 is a conceptual view of an illustrative embodiment of an intersubband transition within a conduction band of a nano-assembly.

FIG. 4 is a graph showing electric field intensity of photons confined in an interface of an illustrative embodiment of the photodetector.

FIG. 5 shows a perspective view of another illustrative embodiment of a photodetector.

FIG. 6 shows the visible light spectrum that may be detected in an illustrative embodiment.

FIG. 7 shows a conceptual view of an illustrative embodiment of an interband transition in a nano-assembly.

FIG. 8 shows an illustrative embodiment of the structure of a ZnO nanobelt.

FIG. 9 shows an illustrative embodiment of energy band diagrams of a nano-assembly of a photodetector.

FIG. 10 shows a cross-sectional view of an illustrative embodiment of the photodetector of FIG. 1.

FIG. 11 shows a cross-sectional view of the illustrative embodiment of the photodetector of FIG. 5.

FIG. 12 shows a perspective view of an illustrative embodiment of a photodetector having nano-assemblies spaced apart from SP waveguides.

FIG. 13 shows a cross-sectional view of the photodetector of FIG. 12.

FIG. 14 shows a cross-sectional view of another illustrative embodiment of a photodetector having nano-assemblies placed in contact with SP waveguides.

FIG. 15 shows a perspective view of an illustrative embodiment of a photodetector for detecting three different spectrum ranges.

FIG. 16 shows a cross-sectional view of the illustrative embodiment of the photodetector shown in FIG. 15.

FIG. 17 shows a cross-sectional view of another illustrative embodiment of a photodetector having nano-assemblies placed in contact with SP waveguides.

FIG. 18 shows a flow diagram of an illustrative embodiment of a method for providing a photodetector that detects long wavelength radiation.

FIG. 19 shows a flow diagram of an illustrative embodiment of a method for providing SP waveguides.

FIG. 20A-20C are a series of diagrams illustrating the method shown in FIG. 19.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.

FIG. 1 shows a perspective view of an illustrative embodiment of a photodetector 100 that may be used to detect long wavelength radiation (e.g., infrared spectrum light). As depicted in FIG. 1, photodetector 100 may be formed on a stacked structure of a substrate 110 and an insulation layer 120. Further, a nano-assembly 130, surface plasmon waveguides (hereinafter referred to as "SP waveguides") 140, a source 150 and a drain 160 may be arranged on insulation layer 120. In one embodiment, at least two SP waveguides 140 are arranged between source 150 and drain 160 which are disposed on proximal and distal ends of the stacked structure, respectively. For example, source 150 and drain 160 may be disposed on proximal and distal ends of insulation layer 120, respectively. When incident light is received, nano-assembly 130 may operate as a channel that interconnects source 150 and drain 160 so that a predetermined current may flow in an external circuit (not shown) coupled to photodetector 100.

SP waveguides 140 may be positioned between source 150 and drain 160 and juxtaposed to nano-assembly 130 in a longitudinal direction of nano-assembly 130. Further, one SP waveguide 140 may be positioned along a first side of nano-assembly 130 and another SP waveguide 140 may be positioned along a second side of nano-assembly 130 that is opposite the first side, defining at least some space between SP waveguides 140 and nano-assembly 130, which may be several to thousands of nanometers. The alternating arrangement of nano-assembly 130 and SP waveguides 140 provides an interface to receive photons from incident light and allows the photons to be effectively confined around nano-assembly 130 between SP waveguides 140, as will be further described below in conjunction with FIG. 4. In one embodiment, the space between SP waveguides 140 and nano-assembly 130 may be filled with a dielectric material such as porcelain (ceramic), mica, glass, plastics, the oxides of various metals, or air, but may include any type of dielectric material. SP waveguides 140 may include any type of metal material such as Ag, Al, Au, Ni, or Ti.

In one embodiment, source 150 and drain 160 may include any metal, silicide, or semiconductors such as silicon, germanium, II-VI semiconductor compounds, or III-V semiconductor compounds. Examples of applicable II-VI semiconductor compounds may include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdZnSe, CdSSe, or ZnSSe, and examples of III-V semiconductor compounds may include GaAs, InP, GaP, AlGaAs, or GaN.

FIG. 2 shows the spectrum of long wavelength radiation that may be detected by photodetector 100. As shown in FIG. 2, long wavelength radiation may include the radiation of light having a wavelength that is more than or equal to several ㎛'s. Detecting such long wavelength radiation is useful in various applications, including both military and civil applications. For example, detection of near-infrared radiation ("NIR" having a wavelength ranging from about 1㎛ to about 3㎛) at room-temperature may be useful for detecting cancer. Detection of mid-infrared radiation ("MIR" having a wavelength ranging from about 3㎛ to about 5㎛) at room-temperature may be applied to many military applications such as seekers in missiles. Detection of infrared radiation ("IR" having a wavelength ranging from about 8㎛ to about 12㎛) at room-temperature may be employed in both military and civil applications for applications such as human body detection. Further, detecting far-infrared ("FIR" having a wavelength of more than several tens of ㎛'s) at room-temperature may be used for narcotics control.

FIG. 3 is a conceptual view of an illustrative embodiment of an intersubband transition within a conduction band of nano-assembly 130. Photodetector 100 may detect long wavelength radiation by using intersubband transitions within a conduction band of nano-assembly 130. As shown in FIG. 3, a conduction band 302 of nano-assembly 130 may have several intersubbands 304 and 306. When a photon having energy corresponding to an intersubband energy gap between intersubbands 304 and 306 impinges on conduction band 302, electrons in conduction band 302 may transition from lower intersubband 304 (i.e., ground state) to upper intersubband 306, causing an electric current through photodetector 100. The photon may have energy in the range of from several meV to hundreds of meV.

FIG. 4 illustrates a graph showing electric field intensity of photons confined in an interface of photodetector 100, which includes SP waveguides 140 and nano-assembly 130 arranged between SP waveguides 140. In FIG. 4, while regions 402 corresponding to SP waveguides 140 include metal material, a region 404 corresponding to nano-assembly 130 include dielectric material, as also shown in FIG. 1. Further, while the x-axis indicates the horizontal position of nano-assembly 130 and SP waveguides 140, the y-axis indicates electric field intensity. The graph shown in FIG. 4 illustrates that a substantial portion of the optical field produced by incident light (i.e., photons) is confined within region 404. The electric field confined between regions 402 and region 404 may be explained by Equation 1 shown below.

[Equation 1]

where D_{x_metal} and D_{x_dielectric} respectively refer to electric displacement fields in region 402 (corresponding to metal material included in SP waveguides 140) and region 404 (corresponding to dielectric material included in nano-assembly 130), E_{x_metal} and E_x-dielectric respectively refer to electric fields in region 402 and region 404, and ε_metal and ε_dielectric respectively refer to the permittivity of region 402 and region 404.

In Equation 1, since the value of ε_metal is much greater than the value of ε_dielectric, E_x-dielectric becomes greater than E_{x_metal}, which means that a substantial portion of the optical field is confined within region 404.

Referring to FIG. 4 and Equation 1, the electric field of the incident photons confined between SP waveguides 140 (i.e., nano-assembly 130) is substantially proportional to the ratio between the permittivity of SP waveguides 140 and the permittivity of nano-assembly 130 (and/or dielectric material filled between SP waveguides 140). Thus, the desired confinement of the electrical field may be obtained by selecting material(s) of appropriate permittivity for SP waveguides 140 and/or nano-assembly 130, even in the case where the width of nano-assembly 130 and/or the height of SP waveguides 140 are smaller than the wavelength of incident photons. In such an embodiment, SP waveguides 140 may be fabricated from one or more various types of metals. As shown in Equation 2 below, the permittivity ε_metal of a metal is a function of frequency and, thus, the type of metal used may depend on the frequency of the photons that are to be detected by photodetector 100. The types of metal may be chosen based on the wavelength to be detected by photodetector 100. In one embodiment, a compound such as Ag, Al, Au, Ni, Ti or any other appropriate metal may be selected for long wavelength detection.

[Equation 2]

where symbol ω_p represents plasma frequency of collective oscillations of the free conduction electrons.

FIG. 5 shows a perspective view of another illustrative embodiment of a photodetector 500 that may be used to detect the visible light spectrum. Photodetector 500 is substantially identical to photodetector 100 except that a transparent gate 180 may be formed above or substantially on top of nano-assembly 130 and SP waveguides 140. An insulation layer 170 may be positioned between transparent gate 180 and nano-assembly 130 (or SP waveguide 140). Although it is shown in FIG. 5 that insulation layer 170 and transparent gate 180 are arranged above nano-assembly 130 and SP waveguides 140 by using supporting members 175, any variety of other suitable structures may be adopted to place insulation layer 170 and transparent gate 180 on nano-assembly 130 and SP waveguides 140. Transparent gate 180 may be positioned substantially perpendicular to nano-assembly 130 and SP waveguide 140 and substantially parallel to the elongated direction of source 150 or drain 160. Transparent gate 180 may be arranged in proximity to at least one nano-assembly 130 and at least two SP waveguides 140 so as to extend substantially parallel to at least one of source 150 and drain 160. Transparent gate 180 functions to reduce the internal field of nano-assembly 130 caused by spontaneous polarization (as will be further described in detail below) of nano-assembly 130.

FIG. 6 illustrates the range of wavelengths in the visible light spectrum that may be detected by photodetector 500. As shown in FIG. 6, the visible light spectrum corresponds to a wavelength range of about 380 to about 780 nm (e.g., corresponding to a color spectrum ranging from violet through red). For example, visible blue light, visible green light, and visible red light have wavelengths of about 450 nm, about 520 nm, and about 650 nm, respectively. Photodetector 500 may detect the visible light spectrum by measuring interband transition of electrons in nano-assembly 130.

FIG. 7 is a conceptual view of an illustrative embodiment of an interband (i.e., band-to-band) transition of electrons between a valence band 702 and a conduction band 704 in nano-assembly 130. When a photon having an energy corresponding to the band gap energy between valence band 702 and conduction band 704 impinges on nano-assembly 130, electrons 706 in valence band 702 may transition to conduction band 704. The transition of electrons 706 from valence band 702 to conduction band 704 (band-to-band transition) causes an electric current to flow through photodetector 500.

FIG. 8 illustrates the basic structure of a ZnO nanobelt 800, which may have a width of about 100 nm and a thickness of about 10 nm. As shown in FIG. 8, the side faces of ZnO nanobelt 800 may include (0001) polar surfaces. In this case, owing to the positive and negative ionic charges on (0001) polar surfaces respectively, spontaneous polarization is induced across ZnO nanobelt 800. As a result, there is an internal field (E) formed along (0001) direction, which minimizes the total energy contribution by spontaneous polarization and degrades the optical transition probability. As shown in FIG. 5, transparent gate 180 may be provided to compensate the internal field (E) in nano-assembly 130 by being arranged above or substantially on top of nano-assembly 130. In one embodiment, insulation layer 170 may be positioned between nano-assembly 130 (and/or SP waveguides 140) and transparent gate 180.

FIG. 9 shows an illustrative embodiment of energy band diagrams of nano-assembly 130 of photodetector 500. The energy band diagram on the left portion in FIG. 9 shows a conduction band in nano-assembly 130 that is obtained if transparent gate 180 does not exist (i.e., is not present) in photodetector 500. Further, the energy band diagram on the right portion of FIG. 9 shows a conduction band in nano-assembly 130 that is obtained if transparent gate 180 does exist (i.e., is present) in photodetector 500. Comparing the two diagrams to each other, an inclination 910 of the energy band diagram (i.e., a lower bound of the conduction band) becomes smaller when transparent gate 180 is provided in photodetector 500 because the internal field in nano-assembly 130 resulting from spontaneous polarization is weakened by applying reverse voltage to transparent gate 180 above or substantially on top of nano-assembly 130. A reverse voltage opposing the direction of the internal field (E) in nano-assembly 130 may be applied from an external circuit (not shown) to transparent gate 180, thereby cancelling the internal field of nano-assembly 130.

FIG. 10 shows a cross-sectional view of photodetector 100 taken along line A-A' in FIG. 1. In FIG. 10, the cross-sectional dimensions of nano-assembly 130 are on the nanometer scale. In some embodiments, nano-assembly 130 may have a width from about 10nm to about 500nm, such as about 10 nm, about 20 nm, about 50nm, about 100nm, about 200nm, or about 500nm, and a length from about 0.5㎛ to about 5㎛, such as about 0.5㎛, about 1㎛, about 2㎛, about 3㎛, about 4㎛ or about 5㎛. In other embodiments, nano-assembly 130 may have a width from about 30nm to about 300nm, a width-to-thickness ratio from about 5 to about 10 and a length of up to a few millimeters. The width and length of nano-assembly 130 may be varied substantially in various embodiments. Nano-assembly 130 may be a nano-wire, a nano-belt, a nano-rod, etc.

In one embodiment, nano-assembly 130 may include semiconductor material (hereinafter referred to as "nano-material") such as Si, InAs, or ZnO. The materials of nano-assembly 130 may be selected depending on the range of radiation wavelength to be detected. Table 1 shows the characteristics (i.e., an intersubband energy gap and a wavelength to be detected) of the nano-materials.

Table 1

Material	Intersubband Energy Gap	Wavelength
ZnO	about 50 meV	about 25㎛
Si	about 100 meV	about 12㎛
InAs	about 300 meV	about 4.5㎛

Referring to Table 1, the wavelengths that may be detected using the nano-materials ZnO, Si, and InAs are about 25㎛, about 12㎛, and about 4.5㎛, respectively. Based on these wavelengths, nano-materials ZnO, Si, and InAs are suitable for detecting FIR, IR, and MIR, respectively. Other appropriate nano-material(s) may be applied to photodetector 100 for detecting the desired wavelength radiation.

In some embodiments, the thickness of SP waveguide 140 ranges from about 2㎛ to about 3㎛ to obtain a fine confinement of the photons. Although SP waveguide 140 is shown as having a rectangular shape in FIGS. 1 and 5, the shape and dimensions of SP waveguide 140 may be varied according to each application. For example, each of SP waveguides 140 may have be a slab, rib or ridge shape for use in photodetector 100 or 500.

FIG. 11 shows a cross-sectional view of photodetector 500 taken along line A-A' in FIG. 5. In one embodiment, nano-assembly 130 may be made from III-V and II-VI semiconductor materials. Table 2 below shows examples of III-V and II-VI semiconductor materials with corresponding band gap energy (eV), the lattice constant (a-axis) in angstroms (Å) and crystal structure.

Table 2

Material	Band gap energy (eV)	Lattice constant (Å)	Crystal structure
CdSe	about 1.732	about 4.2999	wurtzite
CdS	about 2.428	about 4.135	wurtzite
ZnS	about 3.67	about 3.82	wurtzite
MgSe	about 4.05	about 4.15	hexagonal
MgS	about 4.87	about 5.203	rocksalt
ZnO	about 3.44	about 3.25	wurtzite l
MgO	about 7.672	about 4.22	rocksalt
CdO	about 2.28	about 4.69	rocksalt
BeO	about 10.585	about 2.698	wurtzite

The nano-materials of nano-assembly 130 may be selected depending on the range of visible light spectrum to be detected. In one embodiment, nano-assembly 130 may include CdZnS, which is an alloy of CdS and ZnS. CdS and ZnS are direct band gap semiconductor materials and have a hexagonal crystal structure. The band gap energy of Cd_xZn_1-xS may be determined by Equation 3 below.

[Equation 3]

E_g = 3.723-1.241x

When x=0.7, the band gap energy E_g of CdZnS is 2.853eV, which corresponds to an energy of a photon having a wavelength of about 435 nm (blue spectrum light). In one embodiment, where nano-assembly 130 includes Cd_xZn_1-xS (0≤x≤0.5), photodetector 500 may be suitable for detecting the blue spectrum.

In another embodiment, nano-assembly 130 may include CdSSe. CdSSe is an alloy of CdS and CdSe which are direct band gap semiconductor materials and have a hexagonal crystal structure. The band gap energy of CdSe_xS_1-x may be determined by Equation 4 below.

[Equation 4]

E_g = 2.482-0.75x

When x=0.15, the band gap energy E_g of CdSSe is 2.37eV, which corresponds to an energy of a photon having a wavelength of about 520nm (green spectrum light), and when x=0.7, the band gap energy E_g of CdSSe is 1.957eV, which corresponds to an energy of a photon having a wavelength of about 633nm (red spectrum light). That is, nano-assembly 130 including CdSSe may be suitable for detecting both green and red spectrum light. In one embodiment where nano-assembly 130 includes CdSe_xS_1-x (0≤x≤0.4), photodetector 500 may be suitable for detecting green spectrum light. In one embodiment where nano-assembly 130 includes CdSe_xS_1-x (0.6≤x≤1.0), photodetector 500 may be suitable for detecting red spectrum light. Other appropriate nano-materials(s) may be applied to photodetector 500 for detecting a desired spectrum range.

FIG. 12 shows a perspective view of an illustrative embodiment of a photodetector 1200 having nano-assemblies spaced apart from SP waveguides. Referring to FIG. 12, photodetector 1200 includes three nano- assemblies 132, 134 and 136 and four SP waveguides 142, 144, 146 and 148. SP waveguides 144 and 146 may be interposed between nano- assemblies 132, 134 and 136 to create an alternating arrangement of nano- assemblies 132, 134 and 136 and SP waveguides 144 and 146. In one embodiment, nano- assemblies 132, 134 and 136 may each include the same type of nano-material. In this case, photodetector 1200 may be suitable for detecting one specific wavelength range corresponding to the nano-material. By using nano- assemblies 132, 134 and 136, photodetector 1200 may quickly detect a desired wavelength radiation, while collecting more photons from an incident light. In another embodiment, each of nano- assemblies 132, 134 and 136 may include a different type of nano-material. In an illustrative embodiment where nano- assemblies 132, 134 and 136 include different nano-materials (e.g., ZnO, Si, and InAs, respectively), photodetector 1200 may be suitable for detecting different ranges of wavelengths (e.g., FIR, IR, MIR). In this case, a separate drain may be provided for each of nano- assemblies 132, 134 and 136 so that an external circuit connected to each drain can detect different ranges of wavelengths.

FIG. 13 shows a cross-sectional view of photodetector 1200, which is taken along line A-A' of FIG. 12. Referring to FIG. 13, photodetector 1200 has a laminated structure in which a substrate 110, an insulation layer 120, nano- assemblies 132, 134 and 136 (or SP waveguides 142, 144, 146 and 148) are sequentially stacked. In one embodiment, substrate 110 may include glass, silicon or quartz. Insulation layer 120 or 170 may include silicon dioxide (SiO2), a fluorosilicate glass (FSG), a tetraethyl orthosilicate (TEOS) oxide, a silanol (SiOH), a flowable oxide (FOx), a bottom anti-reflective coating (BARC), an anti-reflective coating (ARC), a photoresist (PR), a near-frictionless carbon (NFC), a silicon carbide (SiC), a silicon oxycarbide (SiOC), and/or a carbon-doped silicon oxide (SiCOH). While nano- assemblies 132, 134 and 136 may include nano-material such as Si, InAs, or ZnO, SP waveguides 140 may include any type of metal material including Ag, Al, Au, Ni, or Ti. In FIG. 13, nano- assemblies 132, 134 and 136 are arranged alternatingly with SP waveguides 142, 144, 146 and 148 on insulation layer 120 so that each of nano- assemblies 132, 134 and 136 are spaced apart from its adjacent SP waveguides 142, 144, 146 and 148.

FIG. 14 shows a cross-sectional view of an illustrative embodiment of a photodetector 1400 having nano-assemblies placed in contact with SP waveguides. Referring to FIG. 14, photodetector 1400 includes nano- assemblies 132, 134 and 136 arranged alternatingly and placed into contact with SP waveguides 142, 144, 146 and 148. The alternating arrangement of nano- assemblies 132, 134 and 136 and SP waveguides 142, 144, 146 and 148 as shown in FIG. 14 provides an interface to receive incident light where dielectric media is sandwiched between metal materials.

FIG. 15 shows a perspective view of an illustrative embodiment of a photodetector 1500 having nano-assemblies spaced apart from SP waveguides. Photodetector 1500 includes three nano- assemblies 132, 134 and 136 and four SP waveguides 142, 144, 146 and 148. SP waveguides 144 and 146 may be interposed between nano- assemblies 132, 134 and 136 to create an alternating arrangement of nano- assemblies 132, 134 and 136 and SP waveguides 144 and 146. Further, drains 162, 164 and 166 are separately arranged for each of nano- assemblies 132, 134 and 136. In one embodiment, each of drains 162, 164 and 166 may be connected to different external circuits (not shown) so that a predetermined current through each of nano- assemblies 132, 134 and 136 is detected in the respective external circuits (not shown). In one embodiment, nano- assemblies 132, 134 and 136 may each include different nano-materials, respectively. For example, nano- assemblies 132, 134 and 136 may include Cd_xZn_1-xS (0.5≤x≤1.0), CdSe_xS_1-x (0≤x≤0.4), and CdSe_xS_1-x (0.6≤x≤1.0), respectively. In this case, photodetector 1500 may be suitable for detecting different color spectrums such as blue, green, or red spectrum light.

FIG. 16 shows a cross-sectional view of photodetector 1500, which is taken along line A-A' in FIG. 15. Referring to FIG. 16, photodetector 1500 has a laminated structure in which substrate 110, insulation layer 120, nano- assemblies 132, 134, and 136 (or SP waveguides 142, 144, 146, and 148), insulation layer 170 and transparent gate 180 are sequentially stacked. Substrate 110, insulation layers 120 and 170, source 150 and drain 160 may include the same materials as used in FIG. 11. While nano- assemblies 132, 134 and 136 may include nano-materials such as CdSe, CdS, ZnS, MgSe, or ZnS, SP waveguides 140 and transparent gate 180 may include any type of metal material including Ag, Al, Au, Ni, or Ti. In FIG. 16, nano- assemblies 132, 134 and 136 are arranged alternatingly with SP waveguides 142, 144, 146 and 148 on insulation layer 120 so that each of nano- assemblies 132, 134 and 136 is spaced apart from respective adjacent SP waveguides142, 144, 146 and 148.

FIG. 17 shows a cross-sectional view of an illustrative embodiment of a photodetector 1700 having nano-assemblies placed in contact with SP waveguides. Referring to FIG. 17, photodetector 1700 includes nano- assemblies 132, 134 and 136 arranged alternatingly and placed into contact with SP waveguides 142, 144, 146 and 148. The alternating arrangement of nano- assemblies 132, 134 and 136 and SP waveguides 142, 144, 146 and 148 as shown in FIG. 17 provides an interface to receive incident light where dielectric media is sandwiched between metal materials.

FIG. 18 illustrates a flow-diagram of an illustrative embodiment of a method for providing a photodetector that detects long wavelength radiation. In block 1810, a source and a drain are provided and may be fabricated using any of a variety of well-known fabrication techniques such as chemical vapor deposition, photolithographic, or etching techniques. In block 1820, the source and the drain are coupled by at least one nano-assembly, which may be grown between the source and the drain using any of a variety of suitable techniques such as epitaxial growth techniques, or amorphously deposited by any suitable deposition techniques. Illustrative techniques for applying the coatings include molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD), chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD).

In block 1830, SP waveguides may be provided and positioned juxtaposed to the nano-assembly in a longitudinal direction of nano-assembly so that one of the SP waveguides is positioned along a first side of nano-assembly and another of the SP waveguides is positioned along a second side of nano-assembly that is opposite the first side. FIG. 19 is a flow diagram of an illustrative embodiment of a method for providing SP waveguides. FIGS. 10A-20C are a series of diagrams illustrating the method shown in FIG. 19. Referring to FIG. 19, in block 1910, as shown in FIG. 20A, a first anti-reflection layer 2010 is formed on a photon receiving surface 2012 on insulation layer 120. In one embodiment, photon receiving surface 2012 may be a portion of the top surface of insulation layer 120. In block 1020, as shown in FIG. 20B, first anti-reflection layer 2010 is patterned to define therein two elongated holes 2022 and 2024. For example, first anti-reflection layer 2010 may be patterned by first forming a photo mask with patterns corresponding to two elongated holes 2022 and 2024, etching first anti-reflection layer 2010, and then removing the photo mask. In block 1930, as shown in FIG. 20C, metal is deposited into two elongated holes 2022 and 2024 (shown in FIG. 20B) to respectively form two SP waveguides 2042 and 2044 therein. Such deposition may be performed, for example, by using suitable masking and deposition techniques known in the art. SP waveguides 2042 and 2044 may be obtained by using any of a variety of well-known techniques such as a metal etching.

Referring again to FIG. 18, after positioning the SP waveguides, in block 1840, a transparent gate may be positioned above or substantially on top of the nano-assembly and at least two SP waveguides. In an illustrative embodiment, prior to positioning the transparent gate, an insulation layer may be placed on the nano-assembly and the SP waveguides. In block 1850, the transparent gate is further arranged to be in proximity to at least one nano-assembly and at least two SP waveguides so as to extend substantially parallel to at least one of the source and the drain.

It should be appreciated that, for this and other processes and methods disclosed herein, the functions performed in the processes and methods may be implemented in differing order. Furthermore, the outlined steps and operations are only provided as examples, and some of the steps and operations may be optional, combined into fewer steps and operations, or expanded into additional steps and operations without detracting from the essence of the disclosed embodiments.

The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

With respect to the use of substantially any plural and/or singular terms herein, it should be appreciated that these terms translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It should be further appreciated that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It should be further understood that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, it should be recognized that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It should be further understood that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

In addition, where features or aspects of the disclosure are described in terms of Markush groups, it is recognized that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

It should be further understood, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. It should also be understood that all language such as "up to," "at least," and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, it should also be understood that a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth.

From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims (36)

1. A photodetector capable of detecting long wavelength radiation, comprising:

   a source disposed on a proximal end of an insulation layer;

   a drain disposed on a distal end of the insulation layer;

   at least one nano-assembly coupling the source and the drain between the proximal and distal ends; and

   at least two surface plasmon waveguides positioned between the source and the drain and juxtaposed to the at least one nano-assembly in a longitudinal direction of the at least one nano-assembly,

   wherein one of the at least two surface plasmon waveguides is positioned along a first side of the at least one nano-assembly, and another of the at least two surface plasmon waveguides is positioned along a second side of the at least one nano-assembly that is opposite the first side .
2. The photodetector of Claim 1, wherein at least one of the at least two surface plasmon waveguides is in contact with the at least one nano-assembly.
3. The photodetector of Claim 1, wherein at least one of the at least two surface plasmon waveguides is spaced-apart from the at least one nano-assembly by several to thousands of nanometers.
4. The photodetector of Claim 1, wherein the nano-assembly is configured to have at least one intersubband such that at least one transition of electrons in the at least one intersubband corresponds to detection of a photon.
5. The photodetector of Claim 4, wherein the photon has energy in a range from about several meV to hundreds of meV.
6. The photodetector of Claim 1, wherein a plurality of waveguides and nano-assemblies are disposed so that at least some of the waveguides are interposed between the nano-assemblies to create an alternating arrangement of the waveguides and the nano-assembly.
7. The photodetector of Claim 1, wherein the source and the drain are spaced-apart from each other.
8. The photodetector of Claim 1, wherein the at least one nano-assembly includes at least one of a nanowire, a nanobelt, or a nanorod.
9. The photodetector of Claim 1, wherein the at least one nano-assembly includes an array of at least one of a nano-wire, a nanobelt, or a nanorod.
10. The photodetector of Claim 1, wherein the at least one nano-assembly is selected from the group consisting of ZnO, Si, and InAs.
11. The photodetector of Claim 10, wherein each of the at least one nano-assembly is fabricated from the same material as each other.
12. The photodetector of Claim 1, wherein each of the at least one nano-assembly is fabricated from different types of material.
13. The photodetector of Claim 1, wherein at least one of the at least two surface plasmon waveguides is fabricated from a metal material.
14. The photodetector of Claim 13, wherein the metal material is Ag.
15. The photodetector of Claim 1, wherein the long wavelength radiation has a wavelength of at least 1㎛.
16. The photodetector of Claim 1, wherein the at least one nano-assembly has a width from about 10nm to about 500 nm.
17. The photodetector of Claim 1, wherein the at least one nano-assembly has a length from about 0.5㎛ to about 5㎛.
18. The photodetector of Claim 1, wherein the photodetector is capable of detecting a visible light spectrum, and wherein the photodetector further comprises a transparent gate positioned in proximity to the at least one nano-assembly and the at least two surface plasmon waveguides and further being arranged so as to extend substantially parallel to at least one of the source and the drain.
19. The photodetector of Claim 18, wherein the transparent gate is arranged between the source and the drain.
20. The photodetector of Claim 18, wherein the transparent gate is arranged substantially perpendicular with respect to the at least one nano-assembly.
21. The photodetector of Claim 18, wherein the nano-assembly is configured to have a valence band and a conduction band such that at least one transition of electrons from the valence band to the conduction band corresponds to detection of a photon.
22. The photodetector of Claim 18, wherein the at least one nano-assembly is selected from the group consisting of II-VI semiconductor compounds and III-V semiconductor compounds.
23. The photodetector of Claim 18, wherein the at least one nano-assembly is comprised of Cd_xZn_1-xS, wherein the value of x is from about 0.5 to about 1.0.
24. The photodetector of Claim 18, wherein the at least one nano-assembly is comprised of CdSe_xS_1-x, wherein the value of x is from about 0 to about 0.4.
25. The photodetector of Claim 18, wherein the at least one nano-assembly is comprised of CdSe_xS_1-x wherein the value of x is from about 0.6 to about 1.0.
26. The photodetector of Claim 18, wherein the transparent gate is fabricated from a metal material.
27. The photodetector of Claim 18, wherein the visible light spectrum has a wavelength in the range of from about 300nm to about 800nm.
28. The photodetector of Claim 1, wherein the transparent gate is configured to have a reverse voltage applied thereto so that the internal field of the at least one nano-assembly is reduced thereby.
29. A photodetector capable of detecting a visible light spectrum, comprising:

    a first nano-assembly configured to perform a first spectrum detection;

    a second nano-assembly configured to perform a second spectrum detection;

    a third nano-assembly configured to perform a third spectrum detection;

    a source coupled to a drain by the first, second and the third nano-assemblies;

    at least two surface plasmon waveguides positioned between the source and the drain and juxtaposed to the at least one nano-assembly in a longitudinal direction of the at least one nano-assembly; and

    a transparent gate positioned in proximity to the at least one nano-assembly and the at least two surface plasmon waveguides, and further being arranged to extend substantially parallel to at least one of the source and the drain,

    wherein one of the at least two surface plasmon waveguides is positioned along a first side of the at least one nano-assembly, and another of the at least two surface plasmon waveguides is positioned along a second side of the at least one nano-assembly that is opposite the first side.
30. The photodetector of Claim 29, wherein the color detected by the first nano-assembly is blue.
31. The photodetector of Claim 29, wherein the color detected by the second nano-assembly is green.
32. The photodetector of Claim 29, wherein the color detected by the third nano-assembly is red.
33. A method for assembling a photodetector capable of detecting long wavelength radiation, the method comprising:

    providing a source and drain;

    coupling the source and the drain with at least one nano-assembly; and

    positioning at least two surface plasmon waveguides between the source and the drain and juxtaposing to the at least one nano-assembly in a longitudinal direction of the at least one nano-assembly, and

    wherein one of the at least two surface plasmon waveguides is positioned along a first side of the at least one nano-assembly, and another of the at least two surface plasmon waveguides is positioned along a second side of the at least one nano-assembly that is opposite the first side.
34. The method of Claim33, wherein the at least one nano-assembly is prepared by epitaxial growth techniques.
35. The method of Claim 33, further comprising:

    preparing a substrate; and

    preparing an insulation layer on the substrate, and

    wherein the source and the drain are positioned upon the insulation layer.
36. The method of Claim 33, wherein the photodetector is capable of detecting a visible light spectrum, and wherein the method further comprises positioning a transparent gate in proximity to the at least one nano-assembly and the at least two surface plasmon waveguides.

Images