WO2002043120A2

WO2002043120A2 - Semiconductor laser element and method for producing such a semiconductor laser element

Info

Publication number: WO2002043120A2
Application number: PCT/DE2001/004395
Authority: WO
Inventors: Henning Riechert
Original assignee: Infineon Technologies Ag
Priority date: 2000-11-24
Filing date: 2001-11-22
Publication date: 2002-05-30
Also published as: DE10058444A1; WO2002043120A3

Abstract

The invention relates to a semiconductor laser element that comprises a first semiconductor layer system (102, 103), produced on a substrate (101) by epitaxial growth, of a first material that has a lattice constant that is different from the lattice constant of the substrate. A quantification layer (104) that has a higher lattice constant than the lattice constant of the first semiconductor is produced on the first semiconductor material by epitaxial growth in such a manner that a quantification effect is produced in the quantification layer (104) that suppresses or strongly inhibits the diffusion of the charged particles. A second semiconductor layer system (105, 106, 107) is produced on the quantification layer by epitaxial growth. Nothing to translate

Description

Besehreibung

Semiconductor laser element and method for producing a semiconductor laser element

The invention relates to a semiconductor laser element and a method for producing a semiconductor laser element.

Such a semiconductor laser element and a method for producing a semiconductor laser element are known from [1].

With such a semiconductor laser element, semiconductor layer systems are usually grown on a substrate made of gallium arsenide as a typical combination of materials.

Usually, a first semiconductor layer system with an n-doped layer of aluminum gallium arsenide and ^• further grown on this layer layer of indium gallium arsenide is grown on a substrate layer of gallium arsenide.

A second semiconductor layer system with a layer of gallium arsenide and a p-doped layer of aluminum gallium arsenide grown thereon is grown on the layer of indium gallium arsenide.

A further layer, usually a p-doped layer made of gallium arsenide, is grown on the second semiconductor layer system.

The so-called MBE process (MBE: Molecular Bea Epitaxy) or the process of the so-called organometallic gas phase epitaxy is usually used to grow the various layers.

In molecular beam epitaxy, the layers are deposited by a kind of crystalline condensation of atomic rays or molecular rays on a substrate surface.

The atomic beams are generated by evaporating high-purity starting materials, each corresponding to the layer to be grown, in a purity of usually at least 99.999% in an oven cell.

The particle flow and thus the growth of the individual elements and thus the formation of the respective layer to be grown can be controlled via the temperature of the corresponding furnace cell.

By mixing different atom beams, stoichiometric compound semiconductors can be produced.

Known semiconductor lasers thus consist of compound semiconductors which usually have a lattice constant that is different from the lattice constant of silicon.

The different lattice constants result in dislocations being formed in the grown heterostructures during the epitaxial growth of heterostructures from compound semiconductors on a silicon substrate.

In conventional, planar heterostructures, these dislocations limit the light exploitation and the service life of the semiconductor laser considerably.

The lower efficiency or the shorter lifespan of semiconductor lasers made of compound semiconductors on a substrate made of silicon is due in particular to the fact that free electrical charge carriers in the active region of the laser in which the laser beams are formed in this active region at the above-mentioned ones Dislocations or other crystalline or electrical defects, which are referred to below as defects, are captured and recombine there in a non-radiative manner.

When the electrical charge carriers are recombined, the energy generated is not converted into light, but into heat. The heat generated thus reduces in particular the efficiency and the service life of the semiconductor laser.

For this reason, it is not possible with the method according to the prior art to produce a semiconductor laser element on a silicon substrate with practical efficiency and a sufficient service life.

In [2] it is described that on a silicon material

Quantum dots are grown from a III / V compound semiconductor material, especially indium arsenide. Silicon is in turn applied to the quantum dots.

An overview of colored semiconductor lasers can be found in [3].

[4] describes fundamental aspects of self-ordering quantum dots.

Semiconductor lasers based on quantum dots are described in [5], the quantum wells being formed from a layer structure of aluminum gallium arsenide, gallium arsenide as the quantum dot layer, and again aluminum gallium arsenide.

Another semiconductor laser element is described in [6].

The invention is based on the problem of specifying a semiconductor laser element and a method for producing a semiconductor laser element, in which it is possible to grow heterostructures on a substrate, wherein the lattice constant of the heterostructure and the substrate layer are significantly different from one another, as a result of which the service life of the semiconductor laser element produced is improved compared to the prior art.

The problem is solved by the semiconductor laser element and the method for producing a semiconductor laser element with the features according to the independent patent claims.

A semiconductor laser element has a substrate made of a first material with a first lattice constant.

The substrate can be made of silicon, for example, or also of germanium, gallium phosphide, gallium arsenide, sapphire or silicon carbide.

A first semiconductor layer system with at least one first semiconductor material has been grown on the substrate, the first semiconductor material having a second lattice constant that is not equal to the first lattice constant of the first material.

In the case of silicon as the first material, such a first semiconductor material can be gallium arsenide or an alloy of aluminum gallium arsenide.

Aluminum-gallium phosphide can also be used as the first semiconductor material.

If sapphire or silicon carbide is used as the first material, the first semiconductor material can be an alloy of aluminum _x gallium _x nitride, with 0 <x <1.

The first semiconductor material can also be a material of the general alloy tin-selenium / cadmium-magnesium-zinc-

Selenide-sulfide-telenide based on silicon, germanium or Gallium phosphide or gallium arsenide is grown as the first material of the substrate.

It can be seen from the material combinations shown above that the first semiconductor material has a significantly different lattice constant compared to the lattice constant of the first material of the substrate.

The first semiconductor layer system can have a plurality of semiconductor layers, for example on the first material silicon, germanium or gallium phosphide as substrate material, a layer sequence of indium phosphide grown on the substrate and a semiconductor layer grown thereon from the alloy of the general material matrix indium-y-galliumι_y -Arsenide _z -Phosphidι_ _z , with 0 <y <1 and 0 <z <1, have grown up.

Furthermore, on the substrate of the materials silicon, germanium or gallium phosphide or gallium arsenide, the layer system with the layer of indium phosphide grown directly on the substrate, a layer of indium gallium arsenide grown thereon and a layer of indium Aluminum arsenide.

A first semiconductor layer system comprising a layer of aluminum gallium nitride grown on the substrate, a semiconductor layer made of gallium nitride grown thereon and a layer grown on the gallium nitride layer can be formed on the substrates made of sapphire or silicon carbide

Indium gallium nitride.

On a first material silicon, indium, germanium, gallium phosphide or gallium arsenide as substrate material, for example, an alloy of the general material matrix of cadmium-magnesium-zinc-selenide-sulfide-telenide and one on top of it can be used as the first semiconductor material Layer grown layer of zinc selenide.

According to the invention, a quantization layer made of a quantization material has grown on the first semiconductor layer system, the quantization material having a third lattice constant that is greater than the second lattice constant of the first semiconductor material in the first semiconductor layer system.

The quantization layer is set up in such a way, for example on the basis of the material properties of the quantization material and / or on the basis of the thickness of the quantization layer, that a quantization effect is formed in the quantization layer, as a result of which the electrical charge carriers diffuse to defects in the first semiconductor layer system and / or in the second semiconductor layer system be at least partially prevented.

In the context of this description, the quantization layer denotes a layer in which one or more layers of so-called quantum boxes are formed, that is to say of three-dimensional structures that clearly serve as a three-dimensional potential well with regard to electrical charge carriers, that is to say the movement of electrical charge carriers into every spatial one Impede or at least inhibit direction.

The spreading of the charge carriers is thus achieved in that the quantization layer on the first

Semiconductor material is grown until a thickness is reached at which three-dimensional structures, which represent the quantum boxes, form in the crystal lattice in order to reduce the mechanical stresses generated due to the larger lattice constant. These have a base area which is usually 20 nm wide and are approximately 5 nm high and therefore lead to quantization effects which prevent the electrical charge carriers from spreading in three-dimensional space.

The electrons and holes are thus very efficiently "captured" by the quantum boxes due to the smaller energy band gap with respect to the surroundings of the quantum boxes.

This means that the lateral diffusion of the electrical charge carriers in the active zone of the semiconductor element is considerably reduced since, for example, the mean diffusion length of the electrical charge carriers is reduced by up to a factor of 10.

In this way, the electrical charge carriers can on average be much less likely to be in the crystal lattice of the first semiconductor system or in the crystal lattice of the second

Semiconductor layer system diffuse existing defects or dislocations and thus recombine non-radiating.

Because of the non-radiative recombination locally

Transfers etc. generated heat increases strongly linearly with the number of electric charge carriers recombining at this point, since there is a narrowing of the band gap due to local heating, which results in increased optical absorption, this mechanism of local heating is self-reinforcing, leading to thermal destruction of the semiconductor laser element can result. This is prevented very efficiently by the invention.

An alloy of indium gallium arsenide, gallium arsenide, indium gallium arsenide nitride, cadmium selenide, indium gallium phosphide or, for example, can be used as the quantization material Mercury _m - Cadmiumι._ _m - selenide, with 0 <m <1.

In a method of making a

Semiconductor laser element is grown on a substrate made of a first semiconductor material with a first lattice constant, a first semiconductor layer system made of at least a first semiconductor material, which has a second lattice constant that is not equal to the first lattice constant. The growth can be carried out using the known MBE method.

A quantization layer made of a quantization material with a third lattice constant is grown on the first semiconductor material. The third lattice constant is greater than the second lattice constant of the first semiconductor material of the first semiconductor layer system.

In general, a material can be used as the quantization material for the quantization layer, which has a sufficiently larger lattice constant than the first semiconductor material, so that with a sufficient thickness of the quantization layer, the quantization boxes form from the quantization material in sufficient concentration, i.e. the three-dimensional structures with which free movable electrical charge carriers can be "captured".

It is important to ensure that the quantization material also has a smaller energy band gap than the first semiconductor material.

However, this is usually ensured anyway due to the larger lattice constant of the quantization material compared to the second lattice constant of the first semiconductor material. The Stranski-Krastanov growth mode can be used to grow the quantization layer.

A second semiconductor layer system with a second semiconductor material is grown on the quantization layer. The second semiconductor layer system can be grown on the quantization layer in a correspondingly inverse manner compared to the first semiconductor layer system and correspondingly reverse doping in the case of doped semiconductor layers of the first semiconductor layer system.

An embodiment of the invention is shown in the figures and will be explained in more detail below.

Show it

Figures 1A to 1F cross sections through a

Semiconductor laser element in various manufacturing states during its manufacture.

FIG. 1A shows a semiconductor laser element 100 with an n-doped silicon substrate 101 as the substrate layer.

A first semiconductor layer is on the substrate layer 101

102 grown from n-doped aluminum gallium arsenide by means of the MBE method (see FIG. IB).

The first semiconductor layer 102 made of n-doped aluminum gallium arsenide has a thickness of approximately 2 μm.

A thickness of approximately 150 nm also has a second layer 103 of gallium arsenide grown on the first semiconductor layer 102 (cf. FIG. IC). The gallium arsenide as the first semiconductor material and the aluminum gallium arsenide each have a lattice constant that is considerably larger than the lattice constant of the silicon substrate 101. Then, using the Stranski-Krastanov growth mode, a 1 nm to 3 nm thick layer 104 of indium gallium arsenide is grown as a quantization layer 104 on the gallium arsenide layer 103 (cf. FIG. 1D).

According to an alternative embodiment, the 1 nm to 3 nm thick layer 104 is covered with a 1 nm to 5 nm thick layer of the second material and the layer sequence of the layer 104 made of indium gallium arsenide as the quantization layer 104 and the first nm to 5 nm thick layer of the second material to be repeatedly applied to one another, ie for example growing up so that a layer of the entire thickness of preferably approximately 15 nm is formed.

A further, third semiconductor layer 105, which is a semiconductor layer of the second semiconductor layer system and is produced from gallium arsenide on the quantization layer 104, is produced on the

Quantization layer 104 grew to a thickness of approximately 150 nm (see FIG. 1E).

A fourth semiconductor layer 106 made of p-doped aluminum gallium arsenide is grown on the third semiconductor layer 105 with a thickness of approximately 2 μm (cf. FIG. 1F).

Finally, a protective and contact layer 107 made of p-doped gallium arsenide on the fourth semiconductor layer

106 of the second semiconductor layer system. The protective and contact layer 107 has a thickness of approximately 0.5 µm.

In this context, it should be noted that the individual layers generally have a wider thickness Have a tolerance range in which the thickness can in principle be freely selected.

LIST OF REFERENCE NUMBERS

100 semiconductor laser element

101 silicon substrate

102 First semiconductor layer

103 Second semiconductor layer

104 quantization layer

105 Third semiconductor layer

106 fourth semiconductor layer

107 protective layer

The following publication is cited in this document:

[1] P. Bhattacharya, Semiconductor Optoelectronics Devices, Prentice Hall, ISBN 0-13-495656-7, pp. 55-57, pp. 272-309, 1997

[2] DE 198 19 259 AI

[3] F. Fischer and H.-J. Lugauer, semiconductor lasers bring color into play, Lasers and Optoelectronics, Vol. 28, No. 5, pp. 67 - 73, 1996

[4] M. Grundmann and D. Bimberg, Self-Ordering Quantum Dots: From Solid to Atom, Physikalische Blätter, Vol. 53, No. 6, pp. 517 - 522, 1997

[5] M. Grundmann et al, Novel semiconductor lasers based on quantum dots, lasers and optoelectronics, Vol. 30, No. 3, pp. 70-77, 1998

[6] US 5,898,662

Claims

claims

1. semiconductor laser element with β a substrate made of a first material with a first lattice constant,

A first semiconductor layer system grown on the substrate with at least one first semiconductor material, the lattice constant of the first semiconductor material being not equal to the first lattice constant,

• a quantization layer grown on the first semiconductor material made of a quantization material with a lattice constant that is greater than the lattice constant of the first semiconductor material, • a second semiconductor layer system grown on the quantization layer with a second semiconductor material, β, the quantization layer being set up in such a way that Quantization layer forms a quantization effect, making electrical

Charge carriers are at least partially prevented from diffusing to defects in the first semiconductor layer system and / or in the second semiconductor layer system.

2. The semiconductor laser element according to claim 1, wherein the first semiconductor layer system and / or the second semiconductor layer system has or have a plurality of semiconductor layers.

3. The semiconductor laser element according to claim 2, wherein the first semiconductor layer system has a first semiconductor layer and a second semiconductor layer, wherein the first semiconductor layer is grown on the substrate, and Wherein the second semiconductor layer, which is formed from the first semiconductor material, has grown on the first semiconductor layer.

4. Semiconductor laser element according to one of claims 1 to 3, wherein the substrate comprises at least one of the following materials: ® silicon, ® germanium, • gallium phosphide,

Gallium arsenide,

• sapphire,

® silicon carbide, or

An alloy of at least two of the aforementioned materials.

5. Semiconductor laser element according to one of claims 1 to 4, in which the first semiconductor material comprises at least one of the following materials: ® indium gallium aluminum arsenide,

® gallium arsenide,

Indium gallium aluminum arsenide phosphide, β indium phosphide,

• aluminum _x -GalliuπvL_ _x nitride, with 0 <x <1, o an alloy of at least two of the following materials:

Cadmium, magnesium, zinc, selenium, sulfur, tellurium, beryllium, mercury,

6. Semiconductor laser element according to one of claims 1 to 5, in which the first quantization material comprises at least one of the following materials: ^β indium-y-galliumι_y-arsenide _z -phosphideι_ _z , with 0 <y <1 and 0 <z <1, • Gallium antimonide, β mercury _m cadmium _m selenide, with 0 <m ≤ 1.

7. A method of manufacturing a semiconductor laser element,

In which a first semiconductor layer system with at least one first semiconductor material that has a lattice constant that is not equal to the first lattice constant is grown on a substrate made of a first material with a first lattice constant, β in which one on the first semiconductor layer system

Quantization layer made of a quantization material that has a lattice constant that is greater than the lattice constant of the first semiconductor material,

In which a second semiconductor layer system with a second semiconductor material is grown on the quantization layer,

Wherein the quantization layer is set up in such a way that a quantization effect forms in the quantization layer, as a result of which electrical charge carriers are at least partially prevented from diffusing into defects in the first semiconductor layer system.

8. The method of claim 7, wherein the quantization layer is grown using the Stranski-Krastanov growth mode.