JPH09293932A - Semiconductor light emitting device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive the increase in output power of a semiconductor light emitting device and the attenuation of a threshold current by a method wherein a current is effectively constricted and a reactive current is effectively attenuated. SOLUTION: A laminated semiconductor layer 30, having at least the first conductive type clad layer 4, an active layer 6 and the second conductive type clad layer 8, is formed on a compound semiconductor substrate 1, and a current constriction part 32, which regulates a current passage, is formed at least on a part of the laminated semiconductor layer 30. Crystal defects are preset in high density in this current constriction part 32, and a high resistance region is formed on the interfacial part of the other parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device suitable for application to a II-VI group compound semiconductor laser having a so-called internal stripe structure.

[0002]

2. Description of the Related Art In a semiconductor light emitting device, a stripe-shaped current passage portion, a so-called internal stripe portion structure, is adopted in order to reduce the threshold current I _th . In this case, the current path is limited by providing a current confinement layer for so-called current confinement, that is, a current stop layer, on both sides of the internal stripe portion.
Thus, the structure having the gain guiding function is formed by forming the current confinement layer to concentrate the current in the oscillation region of the active layer and form a large portion of carrier injection, that is, a portion where the gain distribution sharply increases. This current confinement layer is normally formed by selectively forming a high resistance region by implanting protons, boron or other ions, or by forming a current blocking region by a pn junction.

However, such a structure of the current constriction portion does not ensure the current constriction to a sufficient degree, and some reactive current is generated.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to enable effective current confinement and effective reduction of reactive current in a semiconductor light emitting device, for example, a II-VI group compound semiconductor laser. Thus, it is possible to increase the output of a semiconductor light emitting device such as a semiconductor laser and to reduce the threshold current I _th .

Further, according to the present invention, the current constriction portion can be formed with high reproducibility and reliably at a specified position.

[0006]

A semiconductor light emitting device according to the present invention is a laminated semiconductor layer having at least a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer on a compound semiconductor substrate. Is formed, and a current constriction portion that restricts a current path is formed in at least a part of this laminated semiconductor layer. The current constriction portion has a high density of crystal defects, and a high resistance region is formed at the interface with another portion.

In the method for manufacturing a semiconductor light emitting device according to the present invention, a laminated semiconductor layer having at least a first conductivity type clad layer, an active layer, and a second conductivity type clad layer on a compound semiconductor substrate. Has a step of forming
In the step before or during the step of forming this laminated semiconductor layer, a base surface for growth having a crystallinity different from that of the other portion is formed in the portion where the current confinement portion is formed, and a crystal defect is formed thereon. Form a current constriction portion in which a high resistance region is formed at the interface with other portions.

That is, in the present invention, a region having a high crystal defect density is formed as a current constriction portion, and a high resistance generated at the interface between the region having a high crystal defect density and another region, that is, a region having a low crystal defect density. By utilizing the region, it is possible to effectively prevent the current that spreads from the internal stripe portion, that is, the current passage portion to the other portion, thereby avoiding the generation of the reactive current.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor light emitting device according to the present invention, for example, a semiconductor laser, is a laminated structure having at least a first conductivity type clad layer, an active layer, and a second conductivity type clad layer on a compound semiconductor substrate. A semiconductor layer is formed, and a current constriction portion that restricts a current path is formed in at least a part of the laminated semiconductor layer. The current constriction portion has high density of crystal defects and a high density at an interface portion with another portion. A resistance region is formed.

Further, in the method for manufacturing a semiconductor light emitting device according to the present invention for obtaining the semiconductor light emitting device having this structure, at least the first conductivity type cladding layer, the active layer, and the second conductivity type are provided on the compound semiconductor substrate. A step of forming a laminated semiconductor layer having a clad layer, and during or before the step of forming the laminated semiconductor layer, a base surface having a crystallinity different from that of other portions is formed in the current confinement portion forming portion. A current confinement portion is formed in which crystal defects are present at a high density and a high resistance region is formed at the interface with another portion.

Embodiments of a semiconductor light emitting device and a method of manufacturing the same according to the present invention will be described with reference to the drawings. In this example, it is applied to a II-VI group compound semiconductor laser.

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. In this example, as shown in FIG.
A first-conductivity type, for example, n-type II-VI group single crystal substrate 1, for example, ZnSe substrate 1 is prepared, and a current stop is formed on a main surface of the second-conductivity type, for example, p-type III-V group compound semiconductor GaAs layer. Layer 2 is, for example, MBE (Molecular Be
am Epitaxy: First epitaxial growth is performed by the molecular beam epitaxy method. Then, a stripe-shaped opening 2W is formed in the current stop layer 2 at a final portion where a current passage is formed, that is, a portion where an internal stripe portion is formed by, for example, pattern etching by photolithography. In other words, the current stop layer 2 is formed as a base surface below the portion where the current constriction portion is finally formed.

Next, a second epitaxial growth is similarly performed by, for example, MBE. In this second epitaxial growth, first, the first conductivity type straddling the substrate 1 exposed through the opening 2W of the stop layer 2 and the stop layer 2 is the first conductivity type first n-type ZnSSe. 1 clad layer 3 is epitaxially grown, and subsequently, a second conductivity type second clad layer 4 of ZnMgSSe, a first conductivity type guide layer 5 of ZnSSe, an active layer 6 of ZnCdSe, a second Conductivity type In this example, a p-type second conductivity type guide layer 7 made of ZnSSe, for example, a second conductivity type first guide layer made of ZnMgSSe.
Cladding layer 8, for example ZnSSe second conductivity type second cladding layer 9, second conductivity type ZnSe / ZnT, for example
The contact layer 10 having the e superlattice structure and the cap layer 11 of the second conductivity type, for example, ZnTe, are formed by continuous epitaxial growth.

In this case, in the second epitaxial growth for forming the laminated semiconductor layer 30 made of the II-VI group compound semiconductor layer, as shown in FIG. 1, it is formed on the GaAs III-V group compound semiconductor layer by the current stop layer 2. , II- of ZnSe of the substrate 1 facing through the opening 2W
It is formed on the Group VI compound semiconductor layer. By doing so, at least the portion of the laminated semiconductor 30 grown on the current stop layer 2 is of, for example, the first conductivity type at the initial stage of its growth. A stacking fault occurs in a portion extending to the thickness of the clad layer 4, and a region in which crystal defects are present at a high density is formed. In the present invention, this region is used as the current constriction portion 32. That is, in the method of the present invention, the formation of the current constriction portion 32 is performed by forming II in the II-VI group compound semiconductor layer.
By utilizing the difference in reactivity between the -VI group semiconductor surface and the III-V group semiconductor surface, specifically, generation of the stacking fault starting point caused by high reactivity with the III-V group compound semiconductor, On the current stop layer 2 of the III-V group compound semiconductor, stacking faults are selectively generated to form the current confinement portion 32 having high density of crystal defects.

Then, in this case, the substrate 1 made of ZnSe
On the other hand, in the epitaxial growth portion, the stripe portion 31 having excellent crystallinity in which the stacking fault is hardly generated is formed.

As described above, the region having the stacking faults, that is, the crystal defects at a high density is used as the current confinement portion 32. In this case, as already known,
Since a high resistance region is generated at the interface between the portion having high crystal defect density and the portion having few crystal defects, the current confinement portion 32 has an interface with the current stop layer 2 and an interface with the stripe portion 31. A high resistance region is generated at.

On the cap layer 11, for example, Al ₂ O _{3 is used.}
The insulating layer 12 is formed by deposition, and a striped electrode contact window 12W is formed on the striped portion 31 so as to face the striped portion 31.
It is formed by etching by photolithography.

Then, one electrode 13 that makes ohmic contact with the cap layer 11 through the electrode contact window 12W is formed on the insulating layer 12, and the other electrode 14 is ohmicly deposited on the back surface of the substrate 1. .

In this structure, both electrodes 13 and 14 are
When electricity is applied in the meantime, the current stop layer 2 is present and the stripe portion 31 formed on the current stop layer 2 is sandwiched by the current confinement portions 32 having high density of crystal defects.
In addition, the energization is limited, and a large portion of carriers due to current concentration can be formed in a portion of the active layer 6 corresponding to the stripe portion 31, and a portion in which the gain sharply increases is formed. That is, a gain guiding function is generated, and high output and low threshold current are achieved.

According to this structure, the current stop layer 2 is formed, and the stripe portion 31, that is, the current confinement portion 32 in which crystal defects are present at a high density with the current passage interposed, is arranged on the current stop layer 2. In the current confinement part 32, the crystal defect density itself is high, the recombination of carriers is large, and the reactive current is hard to flow, and as described above, there are few crystal defects, that is, crystallinity. Since the high resistance region is generated at the interface with the excellent region, it has an effect of further suppressing the spread of the current from the stripe portion 31, and therefore, the generation of the reactive current is caused.
It can be certainly avoided.

In the semiconductor light emitting device of FIGS. 1 and 2, in this example a II-VI semiconductor laser, at least the first conductivity type cladding layer 4, the active layer 6, and the second conductivity type cladding layer 8 are formed. This is a case where the current constriction portion 32 is formed so as to be located on the side of the substrate 1 of the laminated semiconductor layer 30 that is, but the current confinement portion is formed on the side opposite to the substrate 1. You can also

An example of this case will be described with reference to FIG. Also in this example, the first conductivity type is n-type and the second conductivity type is p-type. In this example, the substrate 1 is made of an n-type III-V group GaAs single crystal.
Then, the laminated semiconductor layer 30 is formed on the substrate 1 by the first epitaxial growth, for example, by the MBE method. In this case, n-type G on the GaAs substrate 1
The first buffer layer 21 made of aAs and the second buffer layer 22 made of n-type II-VI group ZnSe are epitaxially grown on the first buffer layer 21.
First clad layer 3 of the first conductivity type made of SSe, n-type Zn
The first conductivity type second cladding layer 4 made of MgSSe, the first conductivity type guide layer 5 made of n-type ZnSSe, and ZnCdSe.
Active layer 6 made of p-type ZnSSe, guide layer 7 made of p-type ZnSSe, p
-Type ZnMgSSe second conductivity-type first cladding layer 8, p-type ZnSSe second conductivity-type second cladding layer 9, and n-type GaAs III-V group compound semiconductor layer current stop layer 2 are formed by continuous epitaxial growth. First epitaxial growth is performed.

Then, a stripe-shaped opening 2W is formed in the current stop layer 2 at a final portion forming a current path, that is, a portion forming an internal stripe, for example, by pattern etching by photolithography. In other words, the current stop layer 2 is formed at the portion where the current constriction is finally formed.

Next, a second epitaxial growth is performed by, for example, the MBE method. This second epitaxial growth is performed by first exposing the second epitaxial growth through the opening 2W of the stop layer 2.
A second conductivity-type third clad layer 15 made of p-type ZnSSe is epitaxially grown across the conductivity-type second clad layer 9 and a portion on which the current stop layer 2 serves as a base surface, and then this is grown. A contact layer 10 having a p-type ZnSe / ZnTe superlattice structure and a p-type ZnT, for example
The cap layer 11 of e is formed by continuous epitaxial growth.

Also in this case, in the second epitaxial growth using the II-VI group compound semiconductor layer,
It is formed on the GaAs III-V group compound semiconductor layer by the current stop layer 2 and on the II-VI group compound semiconductor layer by ZnSSe exposed through the opening 2W. That is, also in this case, the stripe portion 31 having excellent crystallinity with almost no stacking fault is formed in the epitaxial growth portion of the ZnSSe on the cladding layer 9, but the growth of the GaAs on the stop layer 2 is This is an area where many stacking faults occur. Also in this example, the region having the stacking faults, that is, the crystal defects at a high density is the current constriction portion 32.
Also in this case, since a high resistance region is generated at the interface between the portion having a high crystal defect density and the portion having a small number of crystal defects, the current constriction portion 32 has an interface with the current stop layer 2. A high resistance region is generated at the interface with the stripe portion 31.

On the cap layer 11, for example, Al ₂ O _{3 is used.}
The insulating layer 12 is formed by deposition, and a striped electrode contact window 12W is formed on the striped portion 31 so as to face the striped portion 31.
It is formed by etching by photolithography.

Then, one electrode 13 that makes ohmic contact with the cap layer 11 through the electrode contact window 12W is formed on the insulating layer 12, and the other electrode 14 is ohmicly formed on the back surface of the substrate 1. .

In this structure, both electrodes 13 and 14 are
When electricity is applied in the meantime, the current stop layer 2 is present and the stripe portion 31 formed on the current stop layer 2 is sandwiched by the current confinement portions 32 having high density of crystal defects.
In addition, the energization is limited, and a large portion of carriers due to current concentration can be formed in a portion of the active layer 6 corresponding to the stripe portion 31, and a portion in which the gain sharply increases is formed. That is, the gain guiding function is generated, and the laser emission is performed with the low threshold current I _th .

In this structure as well, the current stop layer 2 is formed, and the stripe portion 31, that is, the current constriction portion 32 in which crystal defects are present at a high density across the current passage is arranged on the current stop layer 2. This current constriction portion 32
In itself, the crystal defect density is high, the recombination of carriers is large, and the reactive current is difficult to flow, and as described above, this and the region with few crystal defects, that is, a region having excellent crystallinity, Since the high resistance region is generated at the interface portion, it has an effect of further suppressing the spread of the current from the stripe portion 31, and thus the generation of the reactive current can be surely avoided.

Epitaxial growth by each MBE method in each of the above-described embodiments can be performed by an MBE apparatus whose schematic configuration diagram is shown in FIG. This MB
The E apparatus has a vacuum chamber 41 equipped with an ultra-high vacuum exhaust device (not shown). In the chamber 41, the epitaxial growth substrate 51, that is, the ZnSe substrate 1 in the example of FIGS. In the example, a substrate holder 42 for holding the GaAs substrate 1 on which the laminated semiconductor layer 30 is formed
Is arranged.

In the chamber 41, a plurality of molecular beam sources 43 which are compound semiconductor material sources are arranged toward the substrate 51. In addition, a plasma generation source 44 for irradiating the chamber 41 with N (nitrogen) plasmatized for the substrate 31.
Is provided. This plasma generation source 44 is, for example, an EC
R (Electron Cyclotron Resonance) cell configuration. The plasma generation source 44 having this ECR cell configuration includes a microwave terminal 4 for supplying microwaves to a plasma generation chamber 44R having a magnet 45.
6 is arranged, and a nitrogen gas introducing pipe 47 for supplying nitrogen gas is provided.

In this manner, the substrate 51 is irradiated with the molecular beam from the molecular beam source 43, so that, for example, II
-VI group compound semiconductor is epitaxy. When p-type II-VI group compound semiconductor by N-doping is epitaxy, in plasma generation source 44,
By applying a magnetic field and a microwave, N gas is turned into plasma by electron cyclotron resonance, and the turned N is turned into a plasma emission port 48 of a plasma generation source 44.
It is made possible to epitaxially grow the N-doped II-VI group compound semiconductor on the substrate 1 by irradiating the substrate with the above molecular beam irradiation. In addition, the chamber 41 is provided with a so-called preliminary chamber 49 for introducing the substrate 51 into and out of the chamber 41.

With this MBE device, each semiconductor layer is epitaxially grown, and the semiconductor light emitting device according to the present invention including the semiconductor light emitting device described in FIGS. 2 and 3 can be constructed.

According to the above-described method of the present invention and the semiconductor light emitting device of the present invention, the stripe-shaped opening 2W is formed under the II-VI compound semiconductor layer or in the II-VI compound semiconductor layer to form the internal stripe portion, that is, Since the current stop layers 2 made of III-V group compound semiconductors having different conductivity types are provided on both sides of the striped current path, the current stop layer 2 itself produces a current constriction effect. II over the top
Since the group VI compound semiconductor layer is formed, stacking faults can be remarkably generated in this portion, so that the crystal defect density is high in this region, that is, both sides of the inner stripe portion, and By forming the current confinement portion 32 that generates a high resistance region between the interface with the region having a low defect density and excellent crystallinity, it is possible to further reduce the reactive current and further enhance the current concentration effect. Can be increased.

The present invention is not limited to the illustrated example, but can be applied to semiconductor light emitting devices such as semiconductor lasers having various configurations. In the above-described example, the first conductivity type is Although the n-type and the second conductivity type are the p-type, the first conductivity type may be the p-type and the second conductivity type may be the n-type.

[0036]

As described above, according to the present invention, with a simple manufacturing method, a current constriction for generating a high resistance region between a region having a high crystal defect density and a low defect density and excellent crystallinity is formed. Since the reactive current can be reduced by forming the portion, high output light emission and low threshold current can be achieved.

Further, according to the manufacturing method of the present invention, when the above-mentioned current constriction portion 32 is formed, it is simply used as a base surface thereof.
Since it is only necessary to form the current stop layer 2, there is no particular increase in the number of operations as compared with the prior art, and the formation of the stripe portion 31 by the current stop layer 2, that is, the positional alignment between the current passage portion and the current constriction portion 32 is performed. Is automatically, that is, self-aligned, so that it is possible to mass-produce the desired semiconductor light emitting device with good reproducibility and thus high yield.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view in a step of an example of a method for manufacturing a semiconductor light emitting device according to the present invention.

FIG. 2 is a schematic cross-sectional view of an example of a semiconductor light emitting device obtained by the manufacturing method of the present invention.

FIG. 3 is a schematic sectional view of another example of the semiconductor light emitting device according to the present invention.

FIG. 4 is a configuration diagram of an example of an MBE device that carries out the manufacturing method of the present invention.

[Explanation of symbols]

1 substrate 2 current stop layer 3 first conductivity type first
Clad layer, 4 first conductivity type second clad layer, 5 first conductivity type guide layer, 6 active layer, 7 second conductivity type guide layer, 8 second conductivity type first clad layer, 9 second conductivity type Second clad layer, 10 contact layer, 11 cap layer, 12 insulating layer, 13, 14 electrode, 15 second conductivity type third clad layer, 30 laminated semiconductor layer, 31 stripe portion, 32 current constriction portion

Claims (4)

[Claims] 1. A compound semiconductor substrate having at least a first conductivity type cladding layer, an active layer, and a second layer.
A laminated semiconductor layer having a conductive clad layer is formed, and a current constriction portion that regulates a current path is formed in at least a part of the laminated semiconductor layer. The current constriction portion has a high density of crystal defects. A semiconductor light emitting device, characterized in that a high resistance region is formed at an interface with another portion. 2. The semiconductor light emitting device according to claim 1, wherein the laminated semiconductor layer is made of a II-VI group compound semiconductor. 3. The method according to claim 1, wherein the compound semiconductor substrate has at least a first
There is a step of forming a laminated semiconductor layer having a conductive type clad layer, an active layer, and a second conductive type clad layer, and the current constriction portion is formed before or during the formation of the laminated semiconductor layer. A base surface is formed in the area where the crystal is formed, where the crystallinity is different from that of the other area, and crystal defects are present at a high density on this, and a high resistance region is formed at the interface with the other area. A method of manufacturing a semiconductor light emitting device, comprising: forming a current constriction portion. 4. The semiconductor according to claim 3, wherein the laminated semiconductor layer is made of a II-VI group compound semiconductor layer, and the underlying surface is a current stop layer made of a III-V group compound semiconductor layer. A method for manufacturing a light emitting device.