JPH02151085A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To improve the confinement of injection carrier without deteriorating luminous efficiency by a method wherein a semiconductor layer arranged between an active layer and a clad layer has a small thickness of about 10Angstrom -200Angstrom , and its band gap energy is set at an intermediate value between the active layer and the clad layer. CONSTITUTION:A double hetero structure is composed of an active layer 4 turning to a light emitting layer, and clad layers 2, 6 which sandwich the active layer 4 and have energy gaps larger than that of the active layer. In this double hetero structure, the title semiconductor light emitting element has semiconductor layers (intermediate clad layers) 3, 5 whose thicknesses are between about 10Angstrom and 200Angstrom , and whose energy gaps have intermediate values between the active layer 4 and the clad layers 2, 6. By this set-up, the confinement of injection carrier is improved without deteriorating the luminous efficiency of the active layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor light emitting device, and particularly to a semiconductor light emitting device having high efficiency and excellent high temperature characteristics.

[Conventional technology]

Conventional high-efficiency semiconductor light emitting devices such as laser diodes and light emitting diodes have a double heterostructure (DH) as shown in Figure 3.
This is an example using a P-based visible light laser diode. FIG. 3(a) is a schematic front view seen from the light emission direction to show the layered structure, and FIG. 3(b) similarly shows an energy band diagram. Gaq, 5 I no, t P active layer 10
3 has a larger energy gap than that (AJo,
It has a double heterostructure sandwiched between 4Ga(,,,,)6.5Ino,5P cladding layers 102 and 104.

[Problem to be solved by the invention]

In order to achieve high efficiency, enable low current operation, and improve high temperature characteristics, it is necessary to have a large energy gap difference between the cladding layer and the active layer. This is to improve the confinement of carriers such as holes in the active layer.Especially at high temperatures, the energy of carriers increases, so the barrier to carriers at the hetero interface between the active layer and the cladding layer is increased. In order to increase the energy gap, it is more important to make the energy gap difference between both layers sufficiently large. However, in general, when the energy gap is made large, deep non-radiative recombination ranks are likely to be generated within the energy gap, and the concentration thereof also increases. In the case of AjiGaInP-based compounds used as visible light emitting device materials, they are used as cladding layers (Afflx G
a1-x). .

In order to increase the energy gap of In□, 5P, the composition of the A1 group must be increased. At this time, a deep non-radiative recombination order is generated and increased within the energy gap. Therefore, in the conventional example described above, if the A1 group composition is increased to increase the energy gap of the cladding layer, AJGaI
An increase in the number of non-radiative recombination centers at the hetero-interface between the nP cladding layer and the G a I n P active layer causes an increase in the non-radiative recombination rate, resulting in a significant decrease in the luminous efficiency in the active layer.

As mentioned above, in the conventional example described above, when trying to increase the energy gap of the cladding layer in order to increase efficiency and enable low current operation or to improve high temperature characteristics, the luminous efficiency in the active layer decreases. This has the disadvantage that the expected effect cannot be obtained and, on the contrary, the device characteristics are deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor light-emitting device that eliminates the above-mentioned drawbacks by utilizing the properties of the material, has high efficiency, is capable of low-current operation, and has excellent high-temperature characteristics.

[Means to solve the problem]

The gist of the present invention is that in a double heterostructure consisting of an active layer serving as a light-emitting layer and a cladding layer with a larger energy gap between the active layer and the cladding layer, the energy gap is larger than about 1 OA and thinner than about 200 Å. The purpose of the present invention is to provide a structure of a semiconductor light emitting device having a semiconductor layer (hereinafter referred to as an intermediate cladding layer) having a gap value intermediate between that of the active layer and the cladding layer between the active layer and the cladding layer. . It is important that the thickness of the semiconductor layer provided between the active layer and the cladding layer is as thin as about 10A to about 200A, and that the bandgap energy value of that layer is an intermediate value between the active layer and the cladding layer. . The target semiconductor light emitting devices are A, RGa I nP system, AjlGaAs system, Affl
The present invention will be described in detail with reference to the energy band diagram shown in FIG. 4. The material may be any material such as GaSb, or a combination of materials may be used. FIG. 4 is an energy band diagram at the hetero interface between the active layer 201 and the cladding layer 202. FIG. 4(a) is a diagram according to the prior art, and FIG. 4(b) is a diagram according to the present invention. When the energy gap difference between the active layer 201 and the cladding layer 202 is increased, the injected carriers 208 having high energy are also bounced off by the hetero field and the surface and are confined in the active layer 201, thereby contributing to light emission. Therefore, improvements in luminous efficiency and high-temperature characteristics are expected. However, as shown in FIG. 4(a), when the 5-cladding layer 202 with a high energy gap is in direct contact with the active layer 201, a hetero-interface occurs, and the L non-radiative recombination center 205 causes a hetero-interface in the active layer 201. Nearby carriers are consumed by the non-radiative recombination process 207, and their contribution to the radiative recombination process 206 decreases, resulting in a decrease in luminous efficiency. Thus, according to the prior art,
Attempting to improve the confinement of injected carriers results in a decrease in luminous efficiency. According to the present invention, a structure with an intermediate cladding layer 210 having a thickness of about 10 to 20 OA sandwiched therein is shown in FIG. 4(b).
It is. A non-radiative recombination center 205 exists between the intermediate cladding layer 210 and the cladding 202 layer with a large energy gap, as shown in the case where the energy gap of the intermediate cladding layer 210 is an intermediate value between the energy gap of the active layer 201 and the cladding layer 202. However, the intermediate cladding layer 21
Because no non-radiative recombination center is generated between 0 and the active layer, carriers in contact with the hetero interface in the active layer also contribute to the radiative recombination 209 as shown in FIG. 4(b). Therefore, even if a semiconductor layer having a composition with a large energy gap is used for the cladding layer, the luminous efficiency of the active layer does not decrease. In addition, the injection carrier 208 with large energy is shown in FIG. 4(b).
As shown in FIG.
1 and contributes to light emission. Thus, according to the present invention, without reducing the luminous efficiency in the active layer,
Confinement of injected carriers can be improved. Furthermore, this makes it possible to improve the efficiency, low current operation, and high temperature characteristics of the semiconductor light emitting device.

〔Example〕

FIG. 1 shows a first embodiment of the present invention. FIG. 3 is a schematic front view of the element as seen from the light emitting direction. A! using GaAs substrate! The present invention is implemented in a 2GaInP visible light semiconductor laser. On the n-GaAs substrate 1, a 1μ thick
n-A of m, Ro.

), 5P cladding layer 2, 50A thick n-(AJ
□, 5 GaO, 5) 0.5 I no, 5 P intermediate cladding layer 5, 1 μm thick p-A, ffo, 5 I
no, 5 P cladding layer 6, p-GaAs cap layer 7
are being gradually grown. Further, a p-type electrode 9 is formed on the 5i02 film 8 on which the striped window 11 is formed, and an n-type electrode is formed directly on the substrate 1, so that a striped current can be injected into the device. The semiconductor light emitting device obtained in this way has an oscillation threshold current value reduced by about 20% and a characteristic temperature improved by about 30% compared to a semiconductor light emitting device obtained by the conventional technology (for example, the device cited in the conventional technology). This enabled low-current operation and improved high-temperature characteristics.

FIG. 2 is a schematic front view of a second embodiment of the present invention, viewed from the light emitting direction of the element. Compared to the first example, (AJx Gat-x ) 0.5In, ), the thickness of the 5P intermediate cladding layer 12.13 is 10OA, and the composition of the A1 group is from the interface with the active layer 4 to the cladding layer 2.6. The difference is that it changes linearly from X=0.4 to X=0.7 as it approaches the interface. The rest is the same as the first embodiment. In this way, compared to the first embodiment, the influence of non-radiative recombination centers on high-energy injected carriers is reduced. Therefore, compared to the first embodiment, the oscillation threshold current value is reduced by about 5% and the characteristic temperature is improved by about 5%, so that a semiconductor light emitting device with even better characteristics can be obtained.

Above, the AJGaInP visible light semiconductor laser has been explained in detail using examples, but other materials, Aff
It can be applied to 1--2 compounds such as lGaAs, A, ffGaSb, and GaInPAs, or II-Vl compounds, and also to combinations thereof. Furthermore, it goes without saying that the present invention can be applied not only to semiconductor lasers but also to general semiconductor light emitting devices including light emitting diodes.

〔Effect of the invention〕

As described above, the present invention makes it possible to improve the confinement of injected carriers without impairing the luminous efficiency of the active layer, thereby realizing a semiconductor light-emitting device with excellent high-temperature characteristics that is capable of higher efficiency and lower current operation than ever before. can.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 respectively show the first embodiment of the present invention. FIG. 3 is a front view and an energy band diagram of the conventional example, and FIG. 4 is an energy band diagram at a hetero interface to show the effect of the present invention. l...-n-G a As substrate, 2...-n-A
Jo, 5I nO, 5P cladding layer, 3·-·n −
(Aio, s Gao, s ) 0.5 I no, st
P intermediate cladding layer, 4,103-...Ga(,,5I
no, 5P active layer, 5-P (AI 0.5G
aQ, 5) 0.5 InO, SP intermediate cladding layer, 6...p Al(3,5I no, 5 P cladding layer, 7-p-GaAs cap layer, 8...5
i02 film, 9... electrode for p type, 10... electrode for n type, 11... striped current injection region, 12-n
(Ajlx Gat-x). 5Ino, 5P intermediate cladding layer, 13・p-(Alx
Ga1-x) 0.5 I no, 5 P intermediate cladding layer, 102・-n −(AJ!□, 4 Gao, 6)
0.5 I no, sP cladding layer, 104...p
-(AJo,4Ga,),6)0.5I nO,5
P cladding layer, 201...active layer, 202...cladding layer, 205...non-radiative recombination center, 206.2
09... Luminescent recombination process, 207... Non-radiative recombination process, 208... High energy injection carrier, 210.
...Intermediate cladding layer.

Claims (1)

[Claims] It has a double heterostructure consisting of an active layer serving as a light emitting region and a cladding layer sandwiching the active layer and having a larger energy gap than the active layer, and has a thickness of about 200 Å thicker than about 10 Å.
1. A semiconductor light emitting device comprising a semiconductor layer between an active layer and a cladding layer, which is thinner than the active layer and having an energy gap value intermediate between the active layer and the cladding layer.