DE10058444A1 - Semiconductor laser element and method for producing a semiconductor laser element - Google Patents

Abstract

The invention relates to a semiconductor laser element that comprises a first semiconductor layer system, produced on a substrate 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 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 that suppresses or strongly inhibits the diffusion of the charged particles. A second semiconductor layer system is produced on the quantification layer by epitaxial growth.

Description

The invention relates to a semiconductor laser element and a Method of manufacturing a semiconductor laser element.

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

In such a semiconductor laser element are usually Semiconductor layer systems on a substrate made of gallium Arsenic grew up as a typical combination of materials.

Usually, a substrate layer made of gallium Arsenide a first semiconductor layer system with an n doped layer of aluminum gallium arsenide and one another layer of indium Gallium arsenide grew up.

A second layer is formed on the indium gallium arsenide layer Semiconductor layer system with a layer of gallium Arsenide and a p-doped layer grown on it grown out of aluminum gallium arsenide.

Another is on the second semiconductor layer system Layer, usually a p-doped layer of gallium Arsenide grew up.

Usually the different layers are grown the so-called MBE method (MBE. Molecular Beam Epitaxy) or the process of the so-called organometallic gas phase epitaxy.

In molecular beam epitaxy, this takes place Layer deposition through a kind of crystalline condensation  of atomic rays or molecular rays on one Substrate surface.

The atomic rays are generated by high purity Starting materials, each in accordance with the growing up Layer, in a purity of usually at least 99.999% can be evaporated in an oven cell.

About the temperature of the corresponding furnace cell, the Particle flow and thus the growth of the individual elements and thus the formation of the respective layer to be grown to be controlled.

By mixing different atomic beams you can stoichiometric compound semiconductors are generated.

Known semiconductor lasers thus consist of Compound semiconductors, which are usually one of the Lattice constant of silicon different lattice constant exhibit.

The different lattice constants mean that the epitaxial growth from heterostructures Compound semiconductors on a silicon substrate in the grown heterostructures dislocations become.

These dislocations limit in conventional, planar Heterostructures the exploitation of light and the lifespan of the Semiconductor laser very significantly.

The lower efficiency or the lower Lifetime of semiconductor lasers from compound semiconductors on a silicon substrate is especially on it attributed to free electrical charge carriers in the active area of the laser in which the laser beams are formed in this active area at the above  Dislocations or other crystalline or electrical Defects, which are referred to as defects below be captured and recombine there without radiation.

When the electrical charge carriers are recombined however, the energy generated is not in light, but in heat implemented. The resulting heat is particularly reduced the efficiency and lifetime of the semiconductor laser.

For this reason it is with the method according to the state of the Technology not possible to put a semiconductor laser element on a Silicon substrate with practical efficiency and a sufficient lifespan.

The invention is therefore based on the problem Semiconductor laser element and a method for manufacturing specify a semiconductor laser element in which it is possible is to grow heterostructures on a substrate, whereby the lattice constant of the heterostructure and the substrate layer are significantly different from each other, making the Lifespan of the semiconductor laser element produced is improved compared to the prior art.

The problem is caused by the semiconductor laser element and the Method for producing a semiconductor laser element with the Features solved according to the independent claims.

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

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

A first semiconductor layer system is also on the substrate grown at least a first semiconductor material, wherein the first semiconductor material has a second lattice constant  which is not equal to the first lattice constant of the first Material is.

Such a first semiconductor material can be used, for example Silicon as the first material, gallium arsenide or one Alloy of aluminum gallium arsenide.

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

If sapphire or silicon carbide is used as the first material, the first semiconductor material can be an alloy of aluminum _x gallium _1-x nitride, with 0 ≦ x ≦ 1.

The first semiconductor material can also be a material of general alloy tin-selenium / cadmium-magnesium-zinc Selenide-sulfide-telenide based on silicon, germanium or Gallium phosphide or gallium arsenide as the first material of the substrate is grown.

From the material combinations shown above is can be seen that the first semiconductor material is a significant has different lattice constant compared to that 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 gallium _{1 -y} -Arsenide _z -phosphide _1-z , with 0 ≦ y ≦ 1 and 0 ≦ z ≦ 1, have grown up.

Furthermore, silicon, Germanium or gallium phosphide or gallium arsenide Layer system with that directly on the substrate  grown layer of indium phosphide, one on top of it grown layer of indium gallium arsenide and one layer of indium aluminum arsenide grown thereon grew up.

On the substrates made of sapphire or silicon carbide first semiconductor layer system from one on the substrate grown layer of aluminum gallium nitride, one semiconductor layer made of gallium nitride and grown thereon a layer grown on the gallium nitride layer Indium gallium nitride.

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

On the first semiconductor layer system is according to the invention a quantization layer made of a quantization material grew up, the quantization material a third Has 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, due to the material properties of the Quantization material and / or due to the thickness of the Quantization layer that is in the quantization layer forms a quantization effect, whereby the electrical Charge carriers at the diffusion to defects in the first Semiconductor layer system and / or in the second Semiconductor layer system at least partially hindered become.  

Within the scope of this description, the Quantization layer denotes a layer in which one or more layers of so-called quantum boxes educate, that is, of three-dimensional structures that vividly with regard to electrical charge carriers as serve three-dimensional potential well, that is the die Movement of electrical charge carriers in every spatial direction hinder or at least inhibit.

The spreading of the charge carriers is thus achieved that the quantization layer on the first Semiconductor material is grown until a thickness is reached is where the breakdown is due to the larger Lattice constant generated mechanical tension in the Form crystal lattice three-dimensional structures that the Represent quantum boxes.

These have a base area which is usually 20 nm wide and are approx. 5 nm high and therefore lead to quantization effects, which the electrical charge carriers at their spread in prevent three-dimensional space.

The electrons are thus made clear by the quantum boxes and holes "captured" very efficiently due to the the environment of the quantum boxes smaller energetic Bandgap.

This means that the lateral diffusion of the electrical Charge carriers in the active zone of the semiconductor element is significantly reduced because, for example, the middle Diffusion length of the electrical charge carriers by up to more reduced as a factor of 10.

In this way, the electrical charge carriers in the Average with a significantly lower probability that in the crystal lattice of the first semiconductor system or in that in the crystal lattice of the second  Semiconductor layer system existing defects or Dislocations diffuse and are therefore non-radiating recombine.

Because of the non-radiative recombination locally Dislocations, etc. generated heat strongly linear with the Number of electrical recombining at this point Charge carriers increase as it is due to local warming the band gap is narrowed, which increases This mechanism entails optical absorption local warming self-reinforcing what up to lead to thermal destruction of the semiconductor laser element can. This is prevented very efficiently by the invention.

For example, an alloy of indium-gallium-arsenide, gallium-arsenide, indium-gallium-arsenide-nitride, cadmium-selenide, indium-gallium-phosphide, or mercury _m -cadmium _1-m- selenide with 0 beispielsweise can be used as the quantization material m ≦ 1.

In a method of making a Semiconductor laser element is made from a substrate a first semiconductor material with a first lattice constant first semiconductor layer system from at least a first Semiconductor material that has a second lattice constant, which is not equal to the first lattice constant. The Can grow up using the known MBE process be performed.

On the first semiconductor material, a Quantization layer made of a quantization material with grew a third lattice constant. The third Lattice constant is larger than the second lattice constant of first semiconductor material of the first Semiconductor layers system.

Generally can be used as a quantization material for the Quantization layer a material can be used that a  sufficiently large lattice constant than the first Has semiconductor material, so that when sufficient Thickness of the quantization layer made of the quantization material form the quantum boxes in sufficient concentration, that is called the three-dimensional structures with which free Movable electrical charge carriers are "captured" can.

Care should be taken that the quantization material also has a smaller energy band gap than that first semiconductor material.

However, this is usually due to the larger ones Lattice constant of the quantization material compared to the second lattice constant of the first semiconductor material anyway guaranteed.

To grow the quantization layer, the Stranski- Krastanov growth mode can be exploited.

A second is on the quantization layer Semiconductor layer system with a second semiconductor material grew up. The second semiconductor layer system can be in accordingly inverse to the first Semiconductor layer system and vice versa Doping with doped semiconductor layers of the first Semiconductor layer system on the quantization layer grow up.

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

Show it

Figs. 1A to 1F are cross sections through a semiconductor laser element to various manufacturing conditions during the manufacture thereof.

Fig. 1A shows a semiconductor laser element 100 with an n-type silicon substrate 101 as a substrate layer.

A first semiconductor layer 102 made of n-doped aluminum gallium arsenide is grown on the substrate layer 101 by means of the MBE method (cf. FIG. 1B).

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. 1C). 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 .

On the gallium arsenide layer 103 of the Stranski-Krastanov growth mode (cf. 1D. Fig.) Is then utilizing a 1 nm to 3 nm thick layer 104 of indium gallium arsenide as Quantisierungsschicht 104 grew.

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 to grow, so that a layer of the entire thickness of preferably approximately 15 nm is formed.

On the Quantisierungsschicht 104 a further, third semiconductor layer 105 is a semiconductor layer of the second semiconductor layers system and is made of gallium arsenide is grown by the MBE method on the Quantisierungsschicht 104 having a thickness of about 150 nm (see. Fig. 1E) ,

On the third semiconductor layer 105, a fourth semiconductor layer is grown 106 microns of p-doped aluminum gallium arsenide having a thickness of about 2 (see. Fig. 1F).

Finally, a protective and contact layer 107 made of p-doped gallium arsenide is grown 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.

It should be noted in this context that the individual Layers in their thickness basically a wide one Have tolerance range in which the thickness is basically free is selectable.  

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

LIST OF REFERENCE NUMBERS

100

Semiconductor laser element

101

Silicon substrate

102

First semiconductor layer

103

Second semiconductor layer

104

Quantisierungsschicht

105

Third semiconductor layer

106

Fourth semiconductor layer

107

protective layer

Claims (10)

1. Semiconductor laser element with
a first semiconductor layer system with at least one first semiconductor material,
a quantization layer made of a quantization material with a lattice constant that is larger than the lattice constant of the first semiconductor material, grown on the first semiconductor material,
a second semiconductor layer system grown on the quantization layer with a second semiconductor material,
wherein the quantization layer is set up in such a way that a quantization effect is formed 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 and / or in the second semiconductor layer system. 2. The semiconductor laser element according to claim 1,
with a substrate made of a first material with a first lattice constant,
in which the first semiconductor layer system has grown on the substrate, the lattice constant of the first semiconductor material being not equal to the first lattice constant, 3. A semiconductor laser element according to claim 1 or 2, in which the first semiconductor layer system and / or the second semiconductor layer system a plurality of semiconductor layers has or have. 4. The semiconductor laser element according to claim 3, 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 formed from the first semiconductor material is grown on the first semiconductor layer. 5. The semiconductor laser element as claimed in one of claims 2 to 4, in which the substrate has 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.

6. The semiconductor laser element according to one of claims 1 to 5, wherein the first semiconductor material comprises at least one of the following materials:

• - indium gallium aluminum arsenide,
• - gallium arsenide,
• - indium gallium aluminum arsenide phosphide,
• - indium phosphide,
• - aluminum _x gallium _1-x nitride, with 0 ≦ x ≦ 1,
• - an alloy of at least two of the following materials:
  Cadmium, magnesium, zinc, selenium, sulfur, tellurium, beryllium, mercury,

7. The semiconductor laser element according to claim 1, wherein the first quantization material comprises at least one of the following materials:

• - indium _y- gallium _1-y- arsenide _z -phosphide _1-z , with 0 ≦ y ≦ 1 and 0 ≦ z ≦ 1,
• - gallium antimonide,
• - Mercury _m- cadmium _1-m- selenide, with 0 ≦ m ≦ 1.

8. A method for producing a semiconductor laser element,
in which, on a first semiconductor layer system with at least one first semiconductor material, a quantization layer made of a quantization material that has a lattice constant that is greater than the lattice constant of the first semiconductor material is grown,
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 such 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. 9. The method according to claim 8, in which on a substrate made of a first material a first lattice constant the first Semiconductor layer system with at least a first Semiconductor material that has a lattice constant that is not equal to the first lattice constant, is grown up, 10. The method according to claim 8 or 9, in which the quantization layer using the Stranski-Krastanov growth mode is growing up.