Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Heterojunction
Patent
1996-03-21
1998-05-12
Davie, James W.
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Heterojunction
257 76, 257 79, 257103, 372 44, 372 45, H01L 3300, H01S 319
Patent
active
057510130
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a light-emitting device made of gallium nitride type compound semiconductor used for semiconductor light-emitting devices such as blue light-emitting diodes and blue semiconductor lasers and a method for producing the same.
BACKGROUND ART
In recent years, it was reported that a semiconductor device using an Al.sub.x Ga.sub.y In.sub.z N (where 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1) type compound semiconductor, which is a III-V-group compound semiconductor containing nitrogen as a V-group element, has outstanding light-emitting characteristics at room temperature. This type of compound semiconductor has been expected to be a material for realizing a blue light-emitting device (e.g., Japanese Journal of Applied Physics 32 (1993) L8-L11). Semiconductor devices having such a gallium nitride type compound semiconductor are obtained by epitaxially growing an n-type semiconductor layer, an i-type semiconductor layer, or a p-type semiconductor layer made of Al.sub.x Ga.sub.1-x N and In.sub.y Ga.sub.1-y N (where 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) on a sapphire substrate.
As a method of epitaxial growth, a Metalorganic Vapor Phase Epitaxy (MOVPE) method, a Molecular Beam Epitaxy (MBE) method, and the like are generally used. For example, the MOVPE method will be briefly described. Organic metal such as trimethylgallium (TMGa; Ga(CH.sub.3).sub.3), trimethylaluminum (TMAl; Al(CH.sub.3).sub.3) and trimethylindium (TMIn; In(CH.sub.3).sub.3) and ammonia (NH.sub.3) gas are supplied as a reaction gas into a reaction chamber in which a sapphire substrate is provided. An AlGaInN type compound semiconductor is epitaxially grown on the sapphire substrate while the surface temperature of the substrate is kept at a high temperature of 700.degree. to 1100.degree. C. At this time, the AlGaInN type compound semiconductor can be controlled so as to have p-type conductivity, i-type conductivity, or n-type conductivity by supplying diethylzinc (DEZn; Zn(C.sub.2 H.sub.5).sub.2), silane (SiH.sub.4) or the like to the reaction chamber.
As a known typical device using an AlGaInN type compound semiconductor, there is a blue light-emitting diode (e.g., Japanese Journal of Applied Physics 32 (1993) L8-L11). This light-emitting diode has a double hetero structure including an active layer made of In.sub.0.05 Ga.sub.0.95 N, to which zinc (Zn) is added. This is because the light-emission wavelength is adjusted to about 0.45 .mu.m. In this manner, only zinc is added to an active layer in the conventional light-emitting diode using an InGaN active layer.
Furthermore, a light-emitting diode having an MIS structure including an active layer made of Al.sub.x Ga.sub.1-x N is reported (Japanese Laid-Open Patent Publication Nos. 4-10665, 4-10666, and 4-10667). In this light-emitting diode, Zn and Si are simultaneously added to an i-type GaN which is to form a light-emitting layer, so as to change the wavelength of the emitted light.
However, these conventional light-emitting diodes have the following problems:
In the case where only Zn is added to an In.sub.y Ga.sub.1-y N layer, a Zn atom pairs off with an intrinsic defect such as vacancy in the In.sub.y Ga.sub.1-y N layer to be stabilized. However, this decreases the emission efficiency because the intrinsic defect becomes a non-radiative center. In addition, the intrinsic defect increases under the application of an electric field, causing adverse effects such as an increased driving current and decreased reliability of the light-emitting device. In particular, these problems become serious in semiconductor lasers requiring high optical density and carrier density. Furthermore, in the case of using Zn as a p-type impurity, a large amount of Zn should be added because of its low activation ratio.
In order to increase the light-emission wavelength, an increase in the In composition of In.sub.y Ga.sub.1-y N used for an active layer is required. For example, the wavelength is desirably in a blue-green region, i.e., about 5
REFERENCES:
patent: 5403773 (1995-04-01), Nitta et al.
patent: 5563422 (1996-10-01), Nakamura et al.
patent: 5578839 (1996-11-01), Nakamura et al.
patent: 5583879 (1996-12-01), Yamazaki et al.
English Translation of International Preliminary Examination Report dated Jul. 25, 1996.
International Search Report mailed Nov. 21, 1995.
Shuji Nakamura et al., P-GaN/N-InGaN/N-GaN Double-Heterostructure Blue-Light Emitting Diodes, Jpn. J. Appl. Phys, vol. 32 (1993) pp. L8-L11, Part 2, No. 1A/B, 15 Jan. 1993.
Adachi Hideto
Ban Yuzaburo
Ishibashi Akihiko
Kidoguchi Isao
Kubo Minoru
Davie James W.
Matsushita Electric - Industrial Co., Ltd.
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