JPS61181185A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To maintain the injection efficiency of carriers while improving luminous efficiency by forming a strain superlattice layer, in which first strain super-thin films, an energy gap thereof is larger than a clad layer and a lattice constant thereof is smaller than the clad layer, and second strain super-thin films having a lattice constant larger than the clad layer are laminated alternately, to at least one side between the clad layer and an active layer. CONSTITUTION:The titled light-emitting element is formed by using a S-doped In0.48Ga0.52P layer and a Zn-doped In0.48Ga0.52P layer as each of an N-type clad layer 11 and a P-type clad layer 12, an In0.21Ga0.79As0.57P0.43 layer as an active layer 14, a GaP layer as a first strain super-thin film 12, an energy gap thereof is larger than the clad layer and a lattice constant thereof is smaller than the clad layer, and an InP layer as a second strain super-thin film 13 having a lattice constant smaller than the clad layer. The film thickness of the GaP layer 12 and the InP layer 13 severally takes 25Angstrom and 20Angstrom , and the number of respective layer is each brought to three layers and two layers. According to such constitution, electrons in the active layer 14 cannot tunnel the energy barriers of the GaP layers 12 in a strain superlattice layer, and function as energy barriers.

Description

DETAILED DESCRIPTION OF THE INVENTION (Fields of Application) The present invention relates to a semiconductor light emitting device conveniently used in optical communications, information processing, etc.

(Prior art and its problems) Light-emitting elements using InP, GaAs, or multi-component mixed crystals include semiconductor lasers and light-emitting diodes. The basic structure of these light emitting devices is a double heterostructure in which n-type and p-type rad layers sandwich an active layer having a smaller energy gap than these clad layers. However, in recent years, it has been found that the amount of energy discontinuity at the lower end of the conduction band between the active layer and the cladding layer affects the emission temperature characteristics of the light emitting device and the oscillation threshold current density of the semiconductor laser. As a countermeasure to this problem, it has been proposed to insert a semiconductor layer between the active layer and the cladding layer, which has a larger energy gap than the cladding layer.On the other hand, it has been proposed to insert a semiconductor layer between the active layer and the cladding layer. Research on heteroepitaxy with different lattices and lattice constants is also underway. A compound semiconductor light emitting device having a strained layer thin film with a large energy gap and different lattice constants in the cladding layer has also been proposed as in Japanese Patent Application No. 104756/1983.

FIG. 2 is a schematic cross-sectional view of a light emitting device having a conventional strained layer with a thin gt-layer. In the figure, 11.15 is an n-type and p-type cladding layer, 21.22 is a strained thin film having a larger energy gap and smaller lattice constant than the cladding layer, and 14 is an active layer. Conventional strain layer thickness g21.22
are arranged adjacent to the active layer 14, p, n! ! !
The electrons injected into the I-cladding layer 11 cross the low energy barrier of the strained layer thin film (semiconductor layer) 21 and enter the active layer 14.
is injected into. However, due to the high barrier of the strained layer thin film 22, the electrons injected into the active layer 14 pass through the p-type cladding layer 15.
cannot be reached. On the other hand, holes simultaneously injected into the ICp type cladding layer 15 are also injected in the opposite direction.

is implanted into the active layer 14. This active layer 14 is injected. The carriers injected into the active layer 14 are
remains and effectively contributes to light emission.

However, in a conventional light emitting device having a strained layer thin film (21, 22), the strain in the strained layer thin film extends to the active layer 14&C, so that the emission intensity is not improved much compared to the increase in carrier injection efficiency, and the life of the device is shortened. There was a problem in that during short and high-temperature operation, distortion due to heat was added and the light emitting characteristics deteriorated.

(Objective of the Invention) An object of the present invention is to solve such problems and provide a semiconductor light emitting device with high carrier injection efficiency and excellent low current operation and high temperature operation.

(Structure of the Invention) The structure of the present invention is a semiconductor light-emitting device having a structure in which a single-layer or multi-layer active layer serving as a light-emitting region is sandwiched between the active layer and a cladding layer having a relatively large energy gap. A strained superlattice layer in which a first strained layer thin film having a larger energy gap and a smaller lattice constant than the cladding layer and a second strained layer fjgPA having a larger lattice constant than the cladding layer are laminated alternately is used as the cladding layer. It is assumed that at least one of the active layers has a lattice constant of 1% ik, and the lattice constant averaged over the thickness of the strained superlattice layer formed by alternately stacking layers with different lattice constants is 0 of the lattice constant of the active layer. .995
It is preferable to have a value in the range of 1.005 times.

(Function of the Invention) According to the structure of the present invention, by arranging a strained ultra-thin film layer having a larger energy gap than the cladding layer between the cladding layer and the active layer, carrier leakage is prevented. By stacking the strained ultra-thin film layer alternately with layers with long lattice constants and layers with short lattice constants, the strain is concentrated in the stacked strained superlattice layers, and the strain is transferred to the cladding layer and the active layer. I tried not to touch the layers. Therefore, the internal strain of the obtained element is alleviated, and the life and temperature characteristics of the element are improved.

In addition, the lattice constant, which is averaged over the film thickness of the strained superlattice layer in which layers with long lattice constants and layers with short lattice constants are laminated alternately, is in the range of 0.995 to 1.005 times the lattice constant of the active layer (lattice matching degree (within ±0.5%).

This has the effect of facilitating crystal growth of the device, preventing strain from reaching the active layer, and increasing the emission intensity of the active layer.

(Example) Next, we will explain the present invention in detail according to the drawings! I will clarify.

FIG. 1 is a schematic cross-sectional view of an element according to an embodiment of the present invention.

In the structure of this embodiment, the NFI cladding layer 11°p and the rad layer 15 are doped with S, 411Gao, and S, respectively.
zP layer, Zn-doped InoisGaoszP#, active layer 14 K Ino, zlGao re AgG,! 1
? The P0.43 layer is applied to the first strained layer thin film 12, which has a larger energy gap and a smaller lattice constant than the cladding layer.
The second strained layer thin film 13KInP layer has a smaller lattice constant than the aP layer and the cladding layer. GaP layer 1
The film thicknesses of InP layer 2 and InP layer 13 are 25A and 20A, respectively.
In addition, the number of layers was 3 and 2, respectively. Because of this structure, electrons in the active layer 14 are transferred to Ga in the strained superlattice layer.
The energy barrier of the P layer 12 cannot be tunneled and acts as an energy barrier (also, the InP layer 13
By setting 20 people, the quantized electron level in the InP layer 13 is located just below the lower end of the barrier conduction band of the GaP layer 12, so the electrons in the n-side cladding layer 11 are transferred to the InP layer 13. easily pass through without being trapped.

This example and a conventional light emitting device having a thin strained layer were fabricated and compared as stripe electrode type semiconductor lasers.The laser of this example had superior external differential quantum efficiency compared to the conventional one, and was identical to the conventional one. The optical output was approximately three times as high at the drive current, and the maximum oscillation temperature was 40°C higher. or,
When a life test was conducted at 50° C. and 55 tnW, the deterioration rate was improved by more than one digit and a long life was confirmed.

In addition, devices are manufactured by changing the film thicknesses of the first strained layer thin film 12 and the second strained layer thin film 13, and the lattice constant averaged by the film thickness of the strained superlattice layer of the device and the active layer are 7 The relationship between otoluminescence intensity (PL intensity) was investigated. As a result, it was found that the larger the difference between the average lattice constant of the strained superlattice layer and that of the active layer 14, the lower the PL intensity. However, the average constant of the strained superlattice layer is 0.995 to 1.
Within the range of 005 times, the PL intensity is almost constant, and within this range, a device with strong emission intensity can be obtained, and furthermore, within this range, a device can be obtained with good reproducibility, which is advantageous in device production. It could be confirmed.

In this example, InGaAs PlIn
A GaP-based light emitting device is used, and the strained superlattice layer t=GaP layer and I
Although it is composed of an nP layer, it is not limited to these compound semiconductors, and may include InGaAsP/InP, AlGaSb/Ga8b
system.

An I/Vl group compound semiconductor may be used, and the strained superlattice layer may also be a compound semiconductor or an elemental semiconductor such as 8i or Ge. In addition, strained superlattice layers were placed on both sides of the active layer.

Only one side may be used, and although the composition and the number of layers of the strained superlattice layer are made symmetrical with respect to the active layer, they are not limited to being symmetrical, and may be asymmetrical. Further, although the active layer serving as one light emitting region is composed of one layer, the effects of the present invention can be fully exhibited even with a multiple quantum well structure.

(Effects of the Invention) As described in detail above, the present invention maintains carrier injection efficiency, which is a special feature of conventional light emitting elements having strained layer thin films, and also improves luminous efficiency and improves luminescent temperature characteristics. Improvement and long life can be realized. Furthermore, the lattice constant averaged over the thickness of the strained superlattice layer is 0.995 to 1.0 of the lattice constant of the active layer.
If the range is set to 0.05 times, custom improvement of even higher luminous efficiency can be realized, while device fabrication becomes easier.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an embodiment of the present invention, and FIG. 2 is a schematic sectional view illustrating a conventional light emitting element. In fig. 11...-nfJ & cladding layer, 12...
・First strained layer thin film, 13... Second strained layer thin film layer, 14... Active layer, 15... P-type cladding layer, 21.22... ...It is a strained layer thin film. Agent Patent Attorney Susumu Uchihara 1. Pa, -・'' Figure 1 Hand 2 Figure

Claims (2)

[Claims] (1) In a semiconductor light emitting device having a structure in which a single or multilayer active layer serving as a light emitting region is sandwiched between a cladding layer having a relatively large energy gap, the active layer has a larger energy gap than the cladding layer and A strained superlattice layer in which a first strained ultrathin film having a smaller lattice constant and a second strained ultrathin film having a larger lattice constant than the cladding layer are alternately laminated is provided at least on one side between the cladding layer and the active layer. A semiconductor light emitting device comprising: (2) The lattice constant, which is averaged over the thickness of the strained superlattice layer in which layers with different lattice constants are alternately laminated, is 0 of the lattice constant of the active layer.
．． The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is in the range of 995 to 1.005 times.