Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Heterojunction
Patent
1995-07-24
1998-04-14
Mintel, William
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Heterojunction
257 18, 257 21, 257 96, 257 97, 359248, 372 43, 372 45, 372 46, H01L 2906, H01L 310328, H01L 310336
Patent
active
057395438
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an optical semiconductive device and more particularly it relates to an optical semiconductive device that can suitably be used as a semiconductor optical amplifier device.
A number of different types of semiconductor laser device are known, including a quantum well type.
FIG. 7 of the accompanying drawings illustrates a known quantum well type laser device comprising an n-type semiconductor substrate 1, on which an n-type clad layer 2, an SCH (separate confinement heterostructure) layer 3, an MQW (multiquantum well) structure 4, an SCH layer 5, a p-type cladding layer 6, a p-type blocking layer 7, an n-type blocking layer 8, a p-type cap layer 9 are sequentially laid to form a multilayer structure. The device further comprises a p-electrode 10 arranged on the upper surface of the p-type cap layer 9 and an n-electrode 11 arranged under the lower surface of the n-type semiconductor 1.
FIG. 8 of the accompanying drawings schematically illustrates the profile of the energy band surrounding the MQW structure 4 of the quantum well type semiconductor laser device of FIG. 7.
If the MQW structure 4 includes a barrier layer 4a and a well layer 4b as shown in FIG. 8, the energy potential of the barrier layer 4a is tower than that, of the cladding layers 2 and 6 so that carriers can be injected into the well layer 4b with an enhanced efficiency. With such a low energy potential of the barrier layer 4a, however, the quantum effect of the quantum well type semiconductor laser device will be inevitably poor.
The energy potential of the barrier layer 4a may be raised to show a profile as shown in FIG. 9 in order to improve the quantum effect of the quantum well type semiconductor laser device and raise the laser performance. However, this improvement is then offset by a lowered efficiency with which carriers are injected into the well layer 4b.
As a major breakthrough in the above identified problem, Reference Document 1 scited below describes a device having an MQW layer structure into which an electric current can be transversally injected. FIG. 10 schematically shows a cross-sectional view of such a device.
Reference document 1: Handout in the 40th Assembly of the Japanese Institute of Applied Physics, Spring 1993, p1055.
The transversal electric current injection type semiconductor laser device as shown in FIG. 10 and described in Reference Document 1 comprises an Fe-doped InP substrate 21, on which a nondoped InP cladding layer 22, an InGaAsP-SCH layer 23, an InGaAs/InAlAs MQW structure 24, an n-InP buried layer 25, a p-InP buried layer 26, an n-InGaAsP cap layer 27 and p-InGaAsP cap layer 28 are sequentially stratified to form a multilayer structure. An n-electrode 29 is arranged on the upper surface of one cap layer 27, while a p-electrode 30 is arranged on the other cap layer 28.
Electrons are injected from the n-InP buried layer 25 while holes are injected from the p-InP buried layer 26 of the transverse electric current injection type semiconductor laser device of FIG. 10.
In the above described transverse electric current injection type semiconductor laser device, since holes that dominate laser oscillation and move in tile plane of the quantum well layer have a large mass and therefore poor mobility, they cannot diffuse smoothly along the injected direction.
When a voltage is transversely applied as forward bias applied to the n-InP buried layer 25, the MQW well structure 24 and the p-InP buried layer 26 of the device, the density distribution pattern of holes in the MQW layer structure 24 shows a profile that declines from the p-side toward the n-side. Such a declining profile of the density distribution pattern of holes is theoretically proved by simulation in Reference Document 2 listed below.
Reference Document 2: Extended Abstracts of the 1992 International Conference on Solid State Devices and Materials, p249.
When the density distribution of holes in the MQW structure 24 is as mentioned above, the density distribution of electrons also follows almo
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Handout for the 40th Assembly of the Japanese Institute of Applied Physics, Spring 1993, p. 1055.
Tan, G. et al., "Feles: A New 2D Software Design Tool for Optoelectronic Devices", Extended Abstracts of the 1992 International Conference on Solid State Devices and Materials, Tsukuba, 1992, pp. 249-251.
Irikawa Michinori
Shimizu Hitoshi
Mintel William
The Furukawa Electric Co. Ltd.
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