JP2005243720A - Semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably extend a wavelength in a GaLnNAs-based semiconductor light-emitting device. <P>SOLUTION: An N superior composition region is formed in an In superior composition region in In and N compositions in the surface direction of a semiconductor active layer 41, and in a region in which In for preventing N from being taken in hardly exists, and N in an GaInNAs-based semiconductor active layer 41 can be stably and fully taken in for improving the wavelength stably in the GaInNAs-based semiconductor active layer 41 of an active layer region layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting device.

  As a light source for an optical access system, a long wavelength light source, for example, a semiconductor laser of 1.28 μm or more, and a pair of 1.3 μm and 1.55 μm semiconductor lasers for coupling with an optical fiber are desired.

The semiconductor laser in this wavelength region is realized mainly by an InGaAsP semiconductor laser using an InP substrate.
However, semiconductor lasers of these materials have a problem that electron confinement to the active layer is weak, temperature characteristics are about 60K, and temperature characteristics are poor.

On the other hand, a semiconductor laser in which GaInNAs is formed as an active layer on a GaAs substrate has been reported to have an example of a temperature characteristic of 200 K or higher, and high temperature operation characteristics have been improved.
Thus, the excellent temperature characteristic eliminates the need for a cooling device in the laser module, thereby realizing an inexpensive and small long-wavelength semiconductor laser device.

Recently, a 1.3 μm band semiconductor laser based on GaInNAs has been actively reported (for example, see Non-Patent Document 1).
However, most of the reports use the growth method based on MBE (Molecular Beam Epitaxy) method, and a 1.3 μm band semiconductor laser with excellent characteristics can be obtained by MOCVD (Metal Organic Chemical Vapor Deposition) with excellent mass productivity. Not. The reason for this is thought to be that N (nitrogen) incorporation efficiency into the growth layer is not sufficiently obtained.
Even in the case of the MBE method, since it is necessary to grow at a low temperature in order to incorporate N, it is difficult to obtain a high quality GaInNAs layer.

On the other hand, a method for producing a long wavelength laser using InGaAs dots on a GaAs substrate has been proposed (Non-Patent Document 2).
However, when quantum dots are used, since the number of states in the ground state is small, when carriers that provide a gain necessary for laser oscillation are injected, the carriers are injected to a higher level and the oscillation wavelength is shortened. Therefore, it is difficult to realize a 1.3 μm band semiconductor laser having excellent characteristics.
1.3μm continuous-wave lasing operation in GaInNAs quantum-well lasers: Nakahara, K .; Kondow, M .; Kitatani, T .; Larson, MC; Uomi, K .; Photonics Technology Letters, IEEE, Volume: 10 Issue: 4, April 1998 Page (s): 487 -488 High characteristic temperature of near 1.3- &mu; m InGaAs / GaAs quantum-dot lasers: Mukai, K .; Nakata, Y .; Otsubo, K .; Sugawara, M .; Yokoyama, N .; Ishikawa, H .; Lasers and Electro-Optics, 2000. (CLEO 2000). Conference on, 7-12 May 2000 Page (s): 363 -364

  It is an object of the present invention to enable a semiconductor light-emitting device that emits light having a long wavelength of at least 1.28 μm or more to be reliably and stably configured by a MOCVD (Metal Organic Chemical Vapor Deposition) semiconductor layer. It is the purpose.

  The present invention is a semiconductor light emitting device having a GaInNAs based semiconductor light emitting element, wherein the GaInNAs based semiconductor active layer of the active layer region layer of the semiconductor light emitting element has an In and N composition in the plane direction of the semiconductor active layer. It has a composition modulation structure in which a dominant composition region and an N dominant composition region are distributed.

In the semiconductor light emitting device according to the present invention described above, the planar pattern of the composition modulation structure has a band pattern or an island pattern.
According to the present invention, in the semiconductor light emitting device according to the present invention described above, at least one main surface of the semiconductor substrate constituting the semiconductor light emitting element is a GaAs substrate having an off angle with respect to the {100} crystal plane. Features.

According to the present invention, in the semiconductor light emitting device according to the present invention described above, at least one principal surface of the semiconductor substrate constituting the semiconductor light emitting element is a GaAs substrate having a {100} crystal plane.
According to the present invention, in the semiconductor light emitting device according to the present invention described above, the GaInNAs-based semiconductor active layer of the active layer region layer is composed of a single layer or a multilayer quantum well layer, and the barrier layer sandwiching the quantum well layer is locally It has a characteristic distortion.

Further, according to the present invention, in the semiconductor light emitting device according to the present invention described above, the In dominant composition region is a region having more In and As than the average composition, and the N dominant composition region has more N and Ga than the average composition. It is a region.
In the semiconductor light emitting device according to the present invention described above, the GaInNAs-based semiconductor active layer of the active layer region layer is composed of a single layer or a multilayer quantum well layer, and the barrier layer sandwiching the quantum well layer is It is characterized by comprising GaInAs, AlGaInAs, AlGaInP, InGaP, GaNAs, GaAsP, and InGaAsP.

In the semiconductor light emitting device according to the present invention described above, the semiconductor light emitting element is a semiconductor light emitting element of 1.28 μm or more.
In the semiconductor light emitting device according to the present invention described above, the semiconductor light emitting element is a MOCVD (Metal Organic Chemical Vapor Deposition) semiconductor layer.
In the semiconductor light emitting device according to the present invention described above, the GaInNAs-based semiconductor active layer includes Sb.

In the GaInNAs semiconductor light emitting device according to the present invention described above, for example, a semiconductor laser, a semiconductor light emitting device having a desired emission wavelength of 1.31 μm and 1.55 μm can be obtained in an optical access system of 1.28 μm or more. It was.
This is because, in the configuration of the present invention, a semiconductor layer composed of GaInNAs or GaInNAsSb that contributes to the determination of the emission wavelength, specifically a single layer in the active layer region layer, or two or more multiple quantum wells (MQW: This is because the semiconductor active layer sandwiched between the barrier layers in the (Multi Quantum Well) structure can sufficiently capture N or N and Sb amounts sufficient to obtain the target long wavelength.
This N incorporation is caused by the formation of an In dominant composition region and an N dominant composition region, specifically, an InAs dominant composition region and a GaN dominant composition region, that is, by segregating In. By forming a region with a small amount of In that inhibits N, the incorporation of N can be carried out sufficiently and stably here.

  That is, in the semiconductor light emitting device of the present invention, the average wavelength composition for the entire region in the GaInNAs-based active layer is a composition that can obtain a target wavelength. As described above, In that inhibits the incorporation of N is reduced. By segregating, the target GaInNAs (Sb) composition can be obtained stably and surely so that necessary and sufficient N can be incorporated into a region with a small amount of In, thereby increasing the wavelength. It can be planned.

  Therefore, by increasing the degree of freedom of the growth conditions such as the growth temperature, the restriction of the formation of GaInNAs by the MBE method as before is avoided, so that the semiconductor layer can be formed by the MOCVD method. And mass productivity can be improved.

An embodiment of a semiconductor light emitting device using a GaInNAs system, that is, GaInNAs or GaInNAsSb as a semiconductor active layer according to the present invention will be described. However, the present invention is not limited to this embodiment.
FIG. 1 is a schematic configuration diagram of an embodiment of a GaInNAs-based semiconductor light emitting device according to the present invention, for example, a semiconductor laser device.
In this embodiment, a first conductivity type cladding layer 2, a first guide layer 3, an active layer region layer 4, a second guide layer 5, and a second conductivity type first cladding are sequentially formed on a semiconductor substrate 1. A layer 6, an etching stop layer 7, a second conductivity type second cladding layer 8, and a second conductivity type cap layer 9 are formed.
The active layer region layer 4 includes a quantum well layer formed of a semiconductor active layer 41 made of GaInNAs or a single layer or two or more layers, and a barrier layer 42 and a barrier layer arranged with the semiconductor active layer 41 interposed therebetween. And the second guide layers 3 and 5 are arranged.
In the example of FIG. 1, an MQW structure in which a GaInNAs-based semiconductor active layer 41 having a three-layer quantum well structure is stacked via a barrier layer 41 is employed.

Further, in this embodiment example, the cap layer 9 and the second conductivity type second cladding layer 8 are etched in the etching stop layer 7 on both sides of the main current path forming portion, leaving a portion as a stripe ridge portion. This is a case in which the insulating layer 10 is formed in the etching groove 10G by etching to a depth reaching the cladding layer 6 by using the decrease in speed.
Then, an opening is formed in the insulating layer 10 on the cap layer (contact layer) 9, and the first and second electrodes 11 and 12 are deposited ohmicly on the cap layer 9 and the back surface of the substrate 1 through the opening. Made up.

An example embodiment of the semiconductor light emitting device will be described in more detail with reference to FIGS. FIG. 2 is a cross-sectional view of the semiconductor stacked structure of the semiconductor light emitting device shown in FIG.
In this embodiment, a GaAs substrate having an off angle of 10 ° from the {100} crystal plane to the A plane (Ga alignment plane) direction is used as the semiconductor substrate 1. The first conductivity type is n-type and the second conductivity type is p-type.

A first conductive cladding layer 2 made of n-type Al _0.47 Ga _0.53 As, for example, having a thickness of 2 μm, and a first guide made of undoped GaAs having a thickness of about 140 nm are sequentially formed on the semiconductor substrate 1 made of the GaAs substrate. Layer 3, active layer region layer 4 of 3QW structure by repetitive stacking of three layers of GaInNAs semiconductor active layer 41 having a quantum well structure of 8 nm thickness and barrier layer 42 of GaAs having a thickness of 180 nm, GaAs having an undoped thickness of 140 nm A second guide layer 5 by p-type, 100 nm thick Al _0.47 Ga _0.53 As second-conductivity-type first cladding layer 6, p-type 100 nm thick GaAs etching stop layer 7, p second conductivity type second cladding layer 8 by _Al 0.47 _{Ga 0.53} As types of thickness 1.4 [mu] m, p-type thickness 0.3 [mu] m G The cap layer 9 by As, is laminated by a continuous MOCVD.

An etching groove 10G having a depth of the etching stop layer 7 is formed on the laminated semiconductor layer from the cap layer 9 side, and a current blocking layer 10 made of, for example, SiO ₂ insulating layer or n-type GaAs is formed in the groove 10G. Thus, a semiconductor light emitting element, that is, a semiconductor laser element is formed.
A plurality of the semiconductor light emitting elements are simultaneously formed on the common substrate 1 and the first and second electrodes are formed as described above, and the respective elements are cut and separated.

  In this way, a main current path is formed in the stripe portion (ridge) sandwiched between the insulating layers 10, and the active layer region layer 4 below the stripe portion operates as a light emitting function portion. The optical resonator length is defined by defining the length of the stripe portion in the extending direction. That is, for example, it is cut to the length of the stripe portion having a resonator length of 350 μm.

  The fracture surface of both end faces of the optical vibrator length can be constituted by a mirror surface by a cleavage plane, for example. Then, a dielectric film or the like set on these end faces, that is, the end faces of the resonators, are set to end faces having a required reflectance. These end faces have, for example, a reflectance of 60% on the front surface which is the main light emitting end face, and have a reflectance of 95%, for example, on the rear end face.

In the semiconductor light emitting device obtained by the above-described configuration, the oscillation wavelength is about 1.47 μm. And when the active layer area | region layer 4 in this semiconductor light-emitting device was observed with TEM (transmission electron microscope), the composition modulation | alteration structure was observed.
This is because the use of an off-substrate as the semiconductor substrate 1 causes microscopic periodic steps on the growth surface of the semiconductor layer, so that In having relatively large atomic movement, that is, migration, segregates in the stepped portion. As a result, an In-dominant composition region is formed by a fine region rich in InAs and As that easily binds to In, and a fine region of GaN in which N is incorporated without being inhibited by In is disposed in the other region. It is considered that a compositionally modulated structure is produced.

  FIG. 3 is a schematic cross-sectional view of the above-described composition modulation structure in the GaInNAs-based semiconductor active layer 41 of the above-described active layer region layer 4. In dominant composition regions 21 extending in the thickness direction of the active layer 41, respectively. And N dominant composition regions 22 are alternately arranged in the surface direction of the active layer 41.

For comparison, the composition modulation structure could not be observed when a so-called just substrate that does not depend on an off-substrate was used as the GaAs substrate, although it had the same configuration as the above-described embodiment according to the present invention. .
From these results, it was found that a light-emitting semiconductor device such as a semiconductor laser with a GaInNAs-based active layer can be made longer by providing a composition modulation structure using an off substrate.
FIG. 4 shows the measurement results of the relationship between the off angle and the PL (Photo Luminescence) wavelength. According to this, the wavelength is increased by increasing the off angle. Incidentally, when grown on a just substrate under the same growth conditions that a wavelength of about 1.435 μm was obtained at an off angle of 10 °, the PL wavelength was about 1.33 μm. That is, it can be seen that the emission wavelength is significantly increased by having the composition modulation structure.

However, the above-described composition modulation structure is not obtained only by using an off substrate, and a so-called just substrate 1 made of, for example, a {100} substrate having a zero off angle can be used.
For example, the barrier layer on the film-forming surface of the GaInNAs-based semiconductor active layer 41, and in the examples of FIGS. By configuring, a strain distribution can be generated in the plane.
Since these materials can change the amount of strain depending on the composition, the barrier layer on the formation surface of the GaInNAs-based semiconductor active layer has a portion where the amount of strain due to this material layer is different, and In segregates in the strained portion. It is also possible to form a composition modulation structure using

  As a structure for localizing strain, for example, InGaAs quantum dots are formed in the above-described barrier layer. About the formation method of this quantum dot, it can be based on a known method. Then, when a GaAs layer as a barrier layer is deposited on the surface where the dots exist, for example, in the MQW structure, and a GaInNAs layer constituting the active layer 41 is deposited thereon, a localized portion of strain due to the dots is obtained. Since it is followed and exists on the formation surface, it is possible to form a segregation of In having a large atomic migration (Migration) at the strain localized portion, and thus a dot portion where InAs is segregated.

  FIG. 5 is a plan view schematically showing the pattern of the In dominant composition region 21 and the N dominant composition region 22 in the GaInNAs-based semiconductor active layer 41 as described above. For example, an off-substrate is used as the base 1 described above. By using it, it is possible to obtain various patterns such as the band-like pattern shown in FIGS. 5A and 5B, or the dot pattern described above as shown in FIG. 5C.

The pattern composition modulation of the In segregation part 21 is preferably a fine structure and not so different in composition. That is, when the period of the composition modulation structure is large and the difference in composition is large, a loss of light emission or the like occurs due to a reduction in the band gap of the active layer region layer, resulting in a decrease in gain. .
The optimum value is selected according to the combination of the period and the composition modulation. For example, the period is preferably 1 μm or less, and the fluctuation of the In composition is preferably 10% or less. The same applies to the dot pattern.

In the above-described embodiment, the so-called edge-emitting semiconductor laser structure is used. However, the present invention is not limited to application to such an edge-emitting semiconductor laser, and is applicable to a surface-emitting laser or the like. You can also. FIG. 6 is a schematic cross-sectional view of an example embodiment of a vertical cavity surface emitting laser (VCSEL) according to the present invention.
In this surface-emitting laser, for example, first and second DBR (Distributed Bragg Reflector) mirrors 52 and 53 are sandwiched between a semiconductor substrate 51 made of a GaAs substrate and the like, as in a normal surface-emitting semiconductor laser. For example, the active layer region layer 54 having an MQW structure is provided. This active layer region layer 54 includes, for example, a quantum well layer formed by a GaInNAs semiconductor active layer 41 and a barrier layer 42 in which an In dominant composition region 21 and an N dominant composition region 22 such as the pattern shown in FIG. 5C are formed. It has an MQW structure.

A surface emitting semiconductor laser formed on a GaAs substrate has few lattice mismatches, and an AlGaAs mirror known as a material suitable for a DBR mirror can be applied.
Therefore, when the semiconductor light emitting device according to the present invention is configured by the active layer region layer 53 by the unique GaInNAs semiconductor active layer, the semiconductor light emitting device having high emission efficiency and high quality, long wavelength, that is, 1.3 μm or more, In the example, the surface emitting semiconductor laser can be realized at a low price.

As described above, in the semiconductor light emitting device according to the present invention, since the GaInNAs-based semiconductor layer has a compositional modulation structure, it is avoided that N incorporation by In is inhibited, so that the GaInNAs or GaInNAsSb layer N uptake efficiency can be increased.
Therefore, N can be easily taken in even by a growth method such as MOCVD. Further, since the growth temperature can be increased also in the MBE method, in this case, a higher quality GaInNAs-based semiconductor layer can be grown.

Thus, the fact that the composition of N can be easily increased means that a GaInNAs-based semiconductor layer can be easily formed without flowing a large amount of N raw material or lowering the growth temperature to a level at which the crystal quality deteriorates. It will be able to grow. That is, the range of selection of growth conditions can be expanded.
In addition, it is known that even with mixed crystals with the same composition, the wavelength is longer due to having a periodic structure, but this makes it longer with a smaller In or N composition than a normal GaInNAs layer. Or become possible.

  Further, the present invention is not limited to the semiconductor light emitting device having the above-described structure, and is not limited to an example applied to a semiconductor laser, a semiconductor light emitting element, or a single semiconductor light emitting device having various structures, The present invention can be applied to various devices such as a semiconductor light emitting device having a large number of light emitting portions, an integrated circuit device, and the like.

It is a schematic sectional drawing of an example of the semiconductor light-emitting device by this invention. It is a schematic sectional drawing in the semiconductor laminated structure of an example of the semiconductor light-emitting device by this invention. It is a schematic sectional drawing of the principal part of the active layer area | region layer of the semiconductor light-emitting device by this invention. It is a curve which shows the measurement result of the relationship between the off angle at the time of using an off board | substrate as a semiconductor substrate which comprises a semiconductor light-emitting device, and the wavelength of PL light emission. A, B, and C are schematic plan views showing examples of the pattern of the composition modulation structure. It is a schematic sectional drawing of an example of the surface emitting type semiconductor light-emitting device by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... 1st conductivity type clad layer, 3 ... 1st guide layer, 4 ... Active layer area | region layer, 41 ... GaInNAs type | system | group semiconductor active layer, 42 ... Barrier layer, 5 ... second guide layer, 6 ... second conductivity type first cladding layer, 7 ... etching stop layer, 8 ... second conductivity type second cladding layer, .... Cap layer, 10 ... Current blocking layer, 10G ... Etching groove, 11 ... First electrode, 12 ... Second electrode, 21 ... In dominant composition region, 22 ... N Dominant composition region, 51 ... Semiconductor substrate, 52 ... First DBR mirror, 53 ... Second DBR mirror

Claims (10)

A semiconductor light emitting device having a GaInNAs semiconductor light emitting element,
In the GaInNAs-based semiconductor active layer of the active layer region of the semiconductor light emitting device, an In dominant composition region and an N dominant composition region are distributed in the composition of In (indium) and N (nitrogen) in the plane direction of the semiconductor active layer. A semiconductor light-emitting device having a composition modulation structure.   The semiconductor light-emitting device according to claim 1, wherein the planar pattern of the composition modulation structure has a band-shaped pattern or an island-shaped pattern.   2. The semiconductor light emitting device according to claim 1, wherein at least one main surface of the semiconductor substrate constituting the semiconductor light emitting element is a GaAs substrate having an off angle with respect to the {100} crystal plane.   2. The semiconductor light emitting device according to claim 1, wherein at least one principal surface of the semiconductor substrate constituting the semiconductor light emitting element is a GaAs substrate having a {100} crystal plane. The GaInNAs-based semiconductor active layer of the active layer region layer is composed of a single layer or a multilayer quantum well layer,
2. The semiconductor light emitting device according to claim 1, wherein the barrier layer sandwiching the quantum well layer has local strain. The In dominant composition region is a region with more In and As than the average composition,
2. The semiconductor light emitting device according to claim 1, wherein the N dominant composition region is a region where N and Ga are larger than an average composition. The GaInNAs-based semiconductor active layer of the active layer region layer is composed of a single layer or a multilayer quantum well layer,
2. The semiconductor light emitting device according to claim 1, wherein the barrier layer sandwiching the quantum well layer is made of GaInAs, AlGaInAs, AlGaInP, InGaP, GaNAs, GaAsP, or InGaAsP.   The semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting element is a semiconductor light-emitting element having a thickness of 1.28 μm or more.   2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting element is an MOCVD (Metal Organic Chemical Vapor Deposition) semiconductor layer.   The semiconductor light emitting device according to claim 1, wherein the GaInNAs semiconductor active layer contains Sb.

Images