JP3302162B2 - Semiconductor light emitting device - Google Patents

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 using a compound semiconductor material, and more particularly, to a semiconductor light emitting device in which a GaN-based material or the like has a high luminance by selecting a material.

[0002]

2. Description of the Related Art GaN, which is one of the group III-V compound semiconductors containing nitrogen, has a large band gap of 3.4 eV and is a direct transition type, and is expected as a material for a short wavelength blue light emitting device. . In a semiconductor light-emitting device using a GaN-based material, the light-emitting layer is usually a p-type layer to which a group II acceptor impurity such as Zn or Mg is added, and uses light emitted from a deep level (light emission center) created by the impurity. are doing.

In this type of semiconductor light emitting device, it is necessary to increase the number of light emitting centers in the light emitting layer in order to suppress the luminance saturation and increase the luminance. If impurities are doped at a high concentration, a large amount of impurities will diffuse from the light emitting layer during film formation. For this reason, there are problems that the luminous efficiency cannot be increased, the lattice defects increase and the quality deteriorates, and the high luminance cannot be achieved.

If the light emitting layer is doped with impurities at a high concentration, the wave functions of the electrons bound to the acceptor overlap each other, and the luminous efficiency is rapidly reduced. When light emission due to transition between donor impurities is used, relatively high concentration doping is possible, but this is inefficient because light emission involves spatial movement of electrons.

[0005] These problems become particularly serious when realizing a green-blue semiconductor laser, and no operation example of a semiconductor laser using a GaN-based material has been reported so far. In addition, since the band gap of GaN corresponds to light emission in the ultraviolet region, selection of a material for the light emitting layer is important for manufacturing a light emitting device in the visible region. Specifically, in order to fabricate a visible light semiconductor laser using a GaN-based material, it is necessary to use a compound semiconductor material lattice-matched to the GaN-based material and having a band gap smaller than that of GaN as a light emitting layer having a double heterojunction structure. However, such materials have not yet been recognized.

[0006]

As described above, conventionally, Ga
In a semiconductor light emitting device using an N-based material for a light emitting layer,
If the impurity concentration is increased in order to increase the number of light emitting centers, there is a problem that the diffusion of impurities from the light emitting layer causes a decrease in luminous efficiency and a decrease in quality due to an increase in lattice defects,
It is difficult to realize high-luminance short-wavelength light emission. At the present time, no material has been recognized that realizes a good heterojunction structure by lattice matching with a GaN-based material instead.

The present invention has been made in view of the above circumstances, and has as its object to realize a good heterojunction structure lattice-matched with a GaN-based material, and to achieve a higher brightness than ever before. To provide a semiconductor light emitting device that can realize the above.

[0008]

The gist of the present invention is GaN
An object is to form a high-quality heterojunction structure by using a compound semiconductor material lattice-matched with a system material and having a band gap narrower than GaN for a light emitting layer.

[0009] The semiconductor light emitting device according to the present invention comprises ZnGe.
N and GaN, AlGaN, GaInN or AlGaI
a light emitting layer comprising a mixed crystal of nN and a heterojunction with the light emitting layer;
And a combined GaN-based material layer .

[0010]

[0011]

When the Ga atoms of GaN are alternately replaced with Group II and Group IV atoms, a crystal having a structure similar to GaN can be obtained. The reason that such a crystal has a clear band structure is that
This is the case when the concentration of the substituted group II and group IV atoms exceeds the degenerate concentration (high enough for impurities to form impurity bands),
Usually, a concentration of 1 × 10 ²⁰ cm ⁻³ or more is required. The properties of these materials are similar to those of the base GaN, and have a direct transition band gap similar to that of substantially the same lattice constant, and it is considered that a heterojunction with GaN can be formed. However, application to a light emitting element requires a direct transition type having a narrower band gap than GaN as a confinement layer.

According to the study of the present inventors, when the atom substituted with Ga has d electrons, the d electron orbitals are mixed with the s electrons and p electron orbitals constituting the valence electrons. It has been found that the band gap is narrowed by matching.
Group II atoms have s orbital d-electron orbitals than group IV atoms.
This effect is particularly pronounced with Group II atoms because they are energetically close to orbitals.

Therefore, a compound semiconductor in which Ga atoms of GaN are alternately substituted with Group II and Group IV atoms is lattice-matched with GaN and has a band gap narrower than that of GaN. The performance of the light emitting element can be greatly improved and light emission in the visible region can be achieved. Also,
The emission wavelength can be changed by forming a mixed crystal with these materials and existing nitrogen-containing group III-V compound semiconductors such as GaN, GaInN, AlGaN, and AlGaInN.

Thus, according to the present invention, a hetero-junction can be formed by lattice matching with a GaN-based material, and a high-luminance light-emitting diode and a green-blue semiconductor laser having an emission wavelength in the visible region and without luminance saturation are realized. It is possible to do.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing an element structure of a blue LED according to a first embodiment of the present invention. Cubic SiC
On a (111) plane of a substrate 11, a Mg-doped p-GaN confinement layer (cladding layer) 12 having a thickness of 1 μm and a thickness of 0.1 μm.
A 5 μm Zn _0.5 Ge _0.5 N light emitting layer (active layer) 13 and a 1 μm thick Si-doped n-GaN confinement layer (cladding layer) 14 are sequentially grown and formed. On the confinement layer 14, for example, an SiO ₂ insulating film 17 having a circular opening for limiting a current-carrying region is formed. The n-side electrode 1 is formed on the insulating film 17 and the confinement layer 14.
5 is formed, and a p-side electrode 16 is formed on the lower surface of the substrate 11.

Here, the characteristic point of this embodiment is that the light emitting layer 13 is obtained by replacing all the group III atoms Ga of GaN, which is a group III-V compound semiconductor, with the group II Zn atoms and the group IV Ge. Is to have a composition. Thereby, the lattice constant of the light emitting layer 13 is substantially equal to that of GaN, and the band gap is narrower than that of GaN. Therefore, a structure in which ZnGeN is sandwiched between GaN is a high-quality double heterojunction structure lattice-matched, and the emission wavelength is longer than that of GaN. When this element was actually energized, it emitted light in the blue region.

As described above, according to this embodiment, a good double hetero junction structure lattice-matched with a GaN-based material can be realized, and a light emitting device in the visible region can be realized. Moreover, since the light emission between the bands by the double hetero junction structure is used and the high quality double hetero junction structure is used, it is possible to achieve a higher brightness than ever before.

The luminous efficiency can be improved by using AlGaN instead of GaN for the confinement layers 12 and 14 in the present embodiment, and the emission wavelength can be shortened by using a mixed crystal of ZnGeN and GaN for the luminescent layer. Is possible. Further, the substrate is not limited to cubic SiC, and hexagonal SiC can also be used.

FIG. 2 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of this embodiment. In the drawing, reference numeral 21 denotes a reaction tube made of quartz, into which a raw material mixed gas is introduced from a gas inlet 22. The gas in the reaction tube 21 is exhausted from the gas exhaust port 23.

A susceptor 24 made of carbon is disposed in the reaction tube 21.
4. The susceptor 24 is induction-heated by the high-frequency coil 25. The temperature of the substrate 27 is measured by a thermocouple 26 shown and controlled by another device.

Mg, Zn, Al, Ga, Si, Ge and N
Each of the raw materials is composed of cyclopentadienyl magnesium (C
p ₂ Mg), dimethyl zinc (DMZ), trimethyl aluminum (TMA), trimethyl gallium (TM
G), silane (SiH ₄ ), germane (GeH ₄ ), and ammonia (NH ₃ ) were used.

Next, a method of manufacturing an LED using the apparatus shown in FIG. 2 will be described. First, the sample substrate 27 (cubic Si
The C substrate 11) is placed on the susceptor 24. High-purity hydrogen is introduced at a rate of 1 l / min through the gas inlet 22 to replace the atmosphere in the reaction tube 21. Next, the gas exhaust port 23 is connected to a rotary pump, the pressure inside the reaction tube 21 is reduced, and the internal pressure is set in the range of 20 to 300 Torr.

Next, after the substrate temperature was raised to 1300 ° C. to clean the substrate surface, the substrate temperature was lowered to 1100 ° C., and TMG, NH ₃ and Cp ₂ Mg were simultaneously introduced, and p-type was added.
A GaN confinement layer 12 is grown. Next, the source gas was switched to DMZ and GeH ₄ , and the ZnGeN ₂ light emitting layer 13 was changed.
Grow. Further, TMG, NH ₃ and SiH ₄ are simultaneously introduced to grow the n-GaN confinement layer 14.

Thereafter, the insulating film 17 is formed by a CVD method or the like.
Is formed, the insulating film 17 is selectively etched by an RIE method or the like to form an opening.
By performing vapor deposition or the like, the configuration shown in FIG. 1 is obtained. (Embodiment 2) FIG. 3 is a sectional view showing an element structure of a semiconductor laser according to a second embodiment of the present invention. Hexagonal Si
An n-SiC cladding layer 32, Zn _0.5
Ge _0.5 N light emitting layer 33 and p-SiC cladding layer 34
Are sequentially grown and formed. On the cladding layer 34, an SiO ₂ insulating film 37 having a stripe-shaped opening is formed. A p-side electrode 35 is formed on the insulating film 37 and the cladding layer 34, and an n-side electrode 36 is formed on the lower surface of the substrate 31.

In this embodiment, hexagonal SiC is used for the cladding layers (confinement layers) 32 and 34 and the substrate 31. In this case, since the strain due to the lattice mismatch remains in the light emitting layer 33, the thickness of the light emitting layer 33 needs to be 30 nm or less.

Even with such a configuration, it is possible to realize a light-emitting layer having a band gap narrower than that of GaN, as in the first embodiment, and to achieve high-luminance light emission in the visible region. The same effect as that of the embodiment can be obtained. In the above configuration, GaN may of course be used instead of SiC for the cladding layers 32 and 34. (Embodiment 3) FIG. 4 is a sectional view showing an element structure of a semiconductor laser according to a third embodiment of the present invention. Hexagonal Si
An n-GaN buffer layer 48 is formed on the C substrate 41,
On top of this, a double heterojunction structure composed of an n-GaN cladding layer 42, a ZnGeGaN light emitting layer 43, and a p-GaN cladding layer 44 is grown and formed. Clad layer 4
4, an SiO ₂ insulating film 4 having a striped opening
7 are formed. A p-side electrode 45 is formed on the insulating film 47 and the cladding layer 44, and an n-side electrode 46 is formed on the lower surface of the substrate 41.

The basic structure is the same as that of the second embodiment, but in this embodiment, the cladding layers 42 and 44 are made of Ga.
N, Zn _0.05 Ge _0.05 Ga _0.9 N was used as the light emitting layer 43. Further, an n-GaN buffer layer 48 was provided between the SiC substrate 41 and the cladding layer 42. This buffer layer 4
Numeral 8 is for alleviating lattice mismatch.

Even with such a configuration, the same effects as those of the first embodiment can be obtained. Further, ZnGeN can be used instead of ZnGeGaN for the light emitting layer 43.

The present invention is not limited to the above embodiments. Although Ga is used as the group III atom in the embodiment, AlGa, GaIn, or AlGaIn can be used instead. Further, another group II atom can be used instead of Zn, and another group IV atom can be used instead of Ge. Further, the element structure is not limited to FIGS. 1, 3, and 4, and can be appropriately changed according to specifications. In addition, various modifications can be made without departing from the scope of the present invention.

[0030]

As described above in detail, according to the present invention, it is possible to realize a high-brightness light emitting diode or a green-blue semiconductor laser having no saturation luminance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an element structure of an LED according to a first embodiment.

FIG. 2 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of the first embodiment.

FIG. 3 is a sectional view showing an element structure of a semiconductor laser according to a second embodiment.

FIG. 4 is a sectional view showing an element structure of a semiconductor laser according to a third embodiment.

[Description of Signs] 11, 31, 41: SiC substrate 12: p-GaN confinement layer (cladding layer) 13, 33: ZnGeN light emitting layer (active layer) 14: n-GaN confinement layer (cladding layer) 15, 16, 35,36,45,46 ... electrode 17,37,47 ... SiO ₂ insulating film 21 ... reaction tube 22 ... gas inlet port 23 ... gas exhaust ports 24 ... susceptor 25 ... RF coil 26 ... thermocouple 27 ... sample substrate 32 ... n-SiC cladding layer 34 p-SiC cladding layer 42 n-GaN cladding layer 43 ZnGeGaN light emitting layer 44 p-GaN cladding layer

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A method according to claim 1, wherein ZnGeN, GaN, AlGaN, Ga
A light-emitting layer composed of a mixed crystal of InN or AlGaInN;
A semiconductor light emitting device comprising the light emitting layer and a GaN-based material layer hetero-joined . 2. The method according to claim 1, wherein the GaN-based material layer has a first conductivity type of G.
an aN-based material layer and a second conductivity type GaN-based material layer are provided.
The light-emitting layer is sandwiched between these GaN-based material layers and
Characterized by having a bull heterojunction structure
The semiconductor light emitting device according to claim 1. 3. The GaN-based material layer is made of GaN or AlG.
2. The semiconductor device according to claim 1, wherein the semiconductor source is aN.
Optical element.