JP2931678B2 - Semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device using an InGaAlP-based material.

[0002]

2. Description of the Related Art In recent years, light emitting diodes using various compound semiconductor materials have been studied. Among them, InGa
A light emitting diode using an AlP-based material has a wavelength of 580 nm.
Since light emission by direct transition is obtained in the range of (yellow) to 690 nm (red), it is expected as a highly efficient light source.

FIG. 3 shows an example of this type of light emitting diode.
Is known. That is, the n-GaAs substrate 3
N-GaAs buffer layer 31, n-InGaAl
A P-cladding layer 32, an undoped InGaP active layer 33 and a p-InGaAlP cladding layer 34 are formed, and a p-InGaP intermediate band gap layer 35 and a p-GaAs contact layer 36 are formed on a part thereof. Then, a p-side electrode 37 is formed on the contact layer 36,
An n-side electrode 38 is formed on the lower surface of the substrate 30.

By the way, in the configuration shown in FIG.
In order to sufficiently confine carriers in the active layer 33 and obtain high luminous efficiency, the Al composition of the cladding layers 32 and 34 must be increased. However, in the p-cladding layer 34, generally, when the Al composition is increased, the carrier concentration cannot be increased.
Has a low carrier concentration. For this reason, the electrode 37
Is injected into the active layer 33 with almost no spread in the p-cladding layer 34, and the light emitting region is formed in the region 39 of the active layer 33 immediately below the electrode 37.
Only. Therefore, when light is extracted in the direction of the upper surface, the electrode 37 blocks the light, which is a factor that reduces the light extraction efficiency.

[0005]

As described above, conventionally, since the carrier concentration of the p-cladding layer on the side opposite to the substrate in the double hetero structure is low, the current injected from the electrode on the light extraction side hardly spreads. And the region immediately below the electrode is a light emitting region. For this reason, the electrode on the light extraction side blocks light from the light emitting region, and this has been a factor of reducing the light extraction efficiency.

The present invention has been made in view of the above circumstances, and an object thereof is to extract light from a light emitting region without being blocked by an electrode on a light extraction side.
It is an object of the present invention to provide a semiconductor light emitting device capable of improving light extraction efficiency.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to make the atomic arrangement of an intermediate band gap layer having an intermediate band gap between a cladding layer and a contact layer larger than the band gap of an ordered active layer. The purpose is to form a band gap and thereby improve the light extraction efficiency.

That is, according to the present invention, InGaAs is formed on a semiconductor substrate.
In a semiconductor light emitting device in which a double hetero structure portion in which an active layer made of an IP material is sandwiched between cladding layers and a contact layer is formed on the double hetero structure portion with an intermediate band gap layer interposed therebetween, The bandgap was formed from an ordered layer with a lattice formed, and the intermediate bandgap layer was formed from a disordered layer in which a natural superlattice disappeared due to impurity diffusion, and the bandgap of the intermediate bandgap layer was made larger than the bandgap of the active layer. It is characterized by:

In a preferred embodiment of the present invention, the substrate is made of n-type GaAs, a p-type intermediate band gap layer is formed on the entire surface of the double heterostructure, and the p-type contact layer is formed as an intermediate band. It is characterized by being selectively formed on the gap layer.

[0010]

According to the present invention, the intermediate band gap layer located on the light extraction side is formed over the entire surface of the double heterostructure portion and is a high-concentration impurity layer formed by diffusion of impurities (for example, An). The spread of current in the layer can be increased, and the light emitting region of the active layer can be sufficiently expanded.

Further, since the active layer is an ordered layer having a natural superlattice formed thereon and the intermediate bandgap layer is a disordered layer in which the natural superlattice has disappeared, the intermediate bandgap layer formed on the light extraction side is not formed. The band gap can be larger than the band gap of the active layer in the ordered state. Therefore, light from the active layer can be extracted without being absorbed by the intermediate band gap layer, and light extraction efficiency can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a schematic structure of a semiconductor light emitting device according to a first embodiment of the present invention. 10 in the figure
Denotes an n-GaAs substrate, on which an n-GaAs buffer layer 11 and n-In _0.5 (Ga _{1 -X 1}
Al _X1 ) _0.5 P clad layer 12, In _0.5 (Ga _{1 -X2} A)
l _X2 ) _0.5 P active layer 13, p-In _0.5 (Ga _1-X1 Al
_X1 ) _0.5 P cladding layer 14 and p-In _0.5 (Ga _{1 -X3}
Al _X3 ) _0.5 P intermediate band gap layer 15 is grown and formed.

Here, the active layer 13 is an ordered layer in which a natural superlattice is formed, and the intermediate band gap layer 15 is a disordered layer in which the natural superlattice has disappeared. It is desirable that the degree of disorder in the disordered layer be greater on the emission end face side than on the substrate side. In addition, Al of InGaAlP
The composition may be in the range of 0.6 ≦ X1 ≦ 1, 0 ≦ X2 <X1, 0 ≦ X3 <X1, and in this embodiment, X1 = 0.6 and X2 = X3 = 0. Depending on the Al composition of the active layer 13, X2 = 0 to X2
= 0.5 to green.

On the intermediate band gap layer 15, p-
The GaAs contact layer 16 is formed in a circular shape. Then, a p-side electrode 17 is formed on the contact layer 16,
An n-side electrode 18 is formed on the back surface of the substrate 10. In the drawing, 19 is a light emitting region, 21 is a region where a p-type impurity is diffused and a natural superlattice is disordered, and 22 is an external output light.

Next, a method of manufacturing the device of the above embodiment will be described. First, n-Ga having a surface orientation of (100)
The layers 11 to 16 are sequentially grown and formed on the As substrate 10 by the MOCVD method. The growth conditions at this time were such that a natural superlattice was formed in the active layer 13 and the intermediate band gap layer 15. These conditions include a growth temperature of 690 to 82
0 ° C., V / III ratio (molar ratio of PH ₃ to group III raw material) 20
0 to 400, growth rate 3 μm / h.

When the p-type intermediate band gap layer 15 is grown, p-type impurities (eg, Zn) are sufficiently introduced so that the natural superlattice of the intermediate band gap layer 15 is extinguished. The concentration of the p-type impurity necessary for eliminating the natural superlattice is 6 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁹ cm ^−3.
It is. The thickness of the intermediate band gap layer 15 is 5 to
20 nm.

Next, the p-side electrode 1 is formed on the contact layer 16.
7, an n-side electrode 18 is formed on the lower surface of the substrate 10,
By selectively etching the electrode 17 and the contact layer 16 so as to leave a circular shape, the structure shown in FIG. 1 is obtained.

With such a configuration, the current injected from the electrode 17 spreads laterally in the high-concentration region 21 of the intermediate band gap layer 15 in which the p-type impurity (Zn) is diffused, and Because of the flow, the light emitting region 19 spreads over the entire active layer. Further, the intermediate band gap layer 1 made of a disordered layer formed on the light extraction side
The band gap of No. 5 is larger than the band gap of the active layer 13 in the ordered state. Therefore, the light from the light emitting region 19 can be extracted without being absorbed by the intermediate band gap layer 15, and the light extraction efficiency can be significantly improved.

According to the experiment conducted by the present inventors, the Zn concentration of the intermediate band gap layer 15 was set to 6 × 10 ¹⁷ c
When it was set to m ^-3 or more, luminous efficiency close to 80% was obtained. In the conventional structure in which Zn is not diffused, it was about 30%.

In this embodiment, the intermediate band gap layer 15 is provided on the entire surface of the p-cladding layer 14, and the intermediate band gap layer 15 is disordered by Zn diffusion. . The diffusion rate of Zn is Al
The smaller the composition ratio, the faster the InGaP layer and InGaAs
It is very different in the 1P layer. Generally, the diffusion rate of the InGaP layer is about five times faster than that of the InGaAlP layer.

Accordingly, in the conventional structure shown in FIG.
When Zn is diffused into the nGaAlP cladding layer, if the Zn is sufficiently diffused into the cladding layer, Zn also diffuses into the InGaP active layer. On the other hand, as in this embodiment, pI
When Zn is diffused into the p-InGaP intermediate bandgap layer 15 on the nGaAlP cladding layer 14, even if it is sufficiently diffused into the intermediate bandgap layer 15, Zn hardly diffuses into the cladding layer. There is no inconvenience such as diffusion of Zn. That is, according to the present embodiment, the controllability of Zn diffusion is easy.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention. 2A is a top view, and FIG. 2B is a sectional view taken along line AA ′ of FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, a plurality of elements shown in FIG. 1 are formed on one substrate. That is, the layers 11 to 16 are grown and formed on the substrate 10 in the same manner as in the first embodiment, and after the electrodes 17 and 18 are formed, the electrodes 17, the contact layer 16 and the intermediate band gap layer 15 are separated from each other by the separation grooves 25. , A plurality of light emitting elements are formed. Here, the contact layer 16 and the electrode 17 have a circular window at the center in each element, contrary to the previous embodiment.

With such a structure, the current can be expanded by the intermediate band gap layer 15 and the light emitting region in the active layer 13 can be expanded as in the previous embodiment. Further, since the contact layer 16 functions as a light separation region by absorbing the light of the individual light emitting elements, and the p clad layer 14 has a large resistance, the current injected from the high concentration region 21
It flows without spreading in the cladding layer 14. For this reason,
The light emitting region 19 can be expanded to a position other than immediately below the electrode, and the light emitting region 19 can be separated.

The present invention is not limited to the above embodiments. In the embodiment, the main surface of the substrate is (100)
However, any substrate may be used as long as the main growth surface is inclined within 15 ° from the {100} plane in the [011] direction. The buffer layer is not limited to GaAs but may be InGaP, GaAlAs, In.
GaAlP or the like may be used. The cladding layer is InGaAl
Not only P alone but also two layers of InGaAlP layer and GaAlAs may be used. The intermediate band gap layer may be made of InGaAlP having a smaller Al composition than the cladding layer, or GaAlAs or InGaP. The active layer is not limited to undoped and may be p-type or n-type. Further, the shape of the p-side electrode is not limited to a circle but may be a polygon. Furthermore, the present invention can be applied not only to a light emitting diode but also to a semiconductor laser, for example, a surface emitting laser in which a current injection direction and a light emission direction are the same. Good. In addition, various modifications can be made without departing from the scope of the present invention.

[0027]

As described above in detail, according to the present invention, by disordering the atomic arrangement of the intermediate bandgap layer having the intermediate bandgap between the cladding layer and the contact layer, the intermediate bandgap layer has an ordered state. A band gap larger than the band gap of the active layer is formed. Accordingly, light from the light emitting region can be extracted without being blocked by the electrode on the light extraction side, and light extraction efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2 is a plan view and a sectional view showing a schematic configuration of a second embodiment of the present invention.

FIG. 3 is a sectional view showing a schematic configuration of a conventional semiconductor light emitting device.

[Explanation of symbols]

10 ... n-GaAs substrate, 11 ... n-GaAs buffer layer, 12 ... n-InGaAlP cladding layer, 13 ... In
GaAlP active layer, 14 ... n-InGaAlP cladding layer, 15 ... p-InGaAlP intermediate band gap layer,
16 ... p-GaAs contact layer, 17 ... n-side electrode, 1
8 ... p-side electrode, 19 ... light-emitting region, 21 ... high-concentration region where impurities are diffused, 22 ... outgoing light, 25 ... element isolation groove

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Genichi Hataoshi 1 Kodamu Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute, Inc. (56) References JP-A-2-98984 (JP, A) Kaihei 1-286481 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 33/00

Claims (1)

(57) [Claims] 1. A semiconductor substrate having InGaAl on the substrate.
A double heterostructure portion formed by sandwiching an active layer made of a P-based material between cladding layers; and a contact layer formed on the double heterostructure portion via an intermediate band gap layer. An ordered layer in which a natural superlattice is formed; the intermediate bandgap layer is a disordered layer in which the natural superlattice has disappeared due to impurity diffusion; and the bandgap of the intermediate bandgap layer is larger than the bandgap of the active layer. A semiconductor light emitting device characterized by having been enlarged.