Active solid-state devices (e.g. – transistors – solid-state diode – With metal contact alloyed to elemental semiconductor type... – In bipolar transistor structure
Reexamination Certificate
2003-03-18
2004-12-14
Mai, Anh Duy (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
With metal contact alloyed to elemental semiconductor type...
In bipolar transistor structure
C257S094000, C257S190000, C257S201000, C438S047000, C372S043010
Reexamination Certificate
active
06831293
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a p-n junction-type compound semiconductor light-emitting device using a group III nitride semiconductor layer containing indium as a light-emitting layer. Specifically, the present invention relates to a p-n junction-type compound semiconductor light-emitting device where an evaporation-preventing layer provided on the light-emitting layer in order to prevent the evaporation of indium from the light-emitting layer is composed of an indirect transition-type boron phosphide (BP)-base semiconductor of a first or a second conduction type.
2. Background Art
Group III nitride semiconductors containing indium, such as gallium indium nitride (Ga
X
In
1−X
N: 0≦X≦1) (indium-containing group III nitride semiconductor), have been heretofore used as a constituent material of a light-emitting layer for emitting short wavelength light such as blue light (see, JP-B-55-3834 (the term “JP-B” as used herein means an “examined Japanese patent publication”)). In order to obtain high-intensity light emission, the light-emitting part usually assumes a double hetero (DH) structure consisting of a light-emitting layer and barrier layers (cladding layers) sandwiching the light-emitting layer. The cladding layer for a Ga
X
In
1−X
N (0≦X≦1) light-emitting layer is conventionally composed of a group III nitride semiconductor such as wurtzite crystal-structure aluminum gallium nitride (Al
X
Ga
1−X
N: 0≦X≦1) intentionally doped with an n-type or a p-type impurity (see, JP-A-6-283825 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)).
However, in a high temperature environment, indium (In) in the Ga
X
In
1−X
N (0≦X≦1) layer evaporates significantly and the indium composition (=1−X) in the layer decreases. In conventional techniques, an “evaporation-preventing” layer for preventing the evaporation of indium is formed on the Ga
X
In
1−X
N (0≦X≦1) light-emitting layer, and a cladding layer such as gallium nitride (GaN) is then provided in a high temperature environment (see, JP-A8-293643). The “evaporation-preventing” layer was heretofore exclusively composed of a group III nitride semiconductor such as direct transition-type wurtzite crystal-structure aluminum gallium nitride (Al
X
Ga
1−X
N: 0≦X≦1) (see, JP-A-5-69236 and JP-A-8-293643).
A technique where a “diffusion-preventing” layer for preventing the impurity doped in the barrier layer from diffusing and penetrating into the light-emitting layer or “evaporation-preventing” layer is provided between the “evaporation-preventing” layer and the barrier layer is also disclosed (see, JP-A-6-283825, supra). In particular, the “diffusion-preventing” layer for preventing magnesium (Mg) from diffusing and penetrating inside the n-type Ga
X
In
1−X
N light-emitting layer from the Mg-doped p-type barrier layer is usually also composed of a group III nitride semiconductor such as direct transition-type aluminum gallium nitride (Al
X
Ga
1−X
N: 0≦X≦1) (see, (1) JP-A-6-283825 supra and (2) JP-A-2001-36196).
Problems in conventional techniques regarding the “evaporation-preventing” layer are attributable to the wurtzite crystal-structure aluminum gallium nitride (Al
X
Ga
1−X
N: 0≦X≦1) constituting the “evaporation-preventing” layer. The wurtzite-structure crystal has a peculiar non-degenerated valence band structure (see, Toshiaki Ikoma and Hideaki Ikoma,
Kagobutsu Handotai no Kiso Bussei Nyumon
(
Guide for Basic Physical Properties of Compound Semiconductor
), 1st ed., page 17, Baifukan (Sep. 10, 1991)) and is conduction cannot be readily formed. For obtaining a low-resistance p-type group III nitride semiconductor layer, the wurtzite-structure crystal must be subjected to a heat treatment so as to eliminate a hydrogen atom (proton) (see, JP-A-5-183189). When an “evaporation-preventing” layer to be disposed between a barrier layer and a light-emitting layer composed of an indium-containing group III nitride semiconductor cannot be readily constructed on the light-emitting layer from a low-resistance electrically conducting layer, for example, a light-emitting diode (LED) having a low forward voltage (so-called V
f
) cannot be readily provided. In addition, a laser diode (LD) having a low threshold voltage (so-called V
th
) cannot be readily provided.
In a direct transition-type semiconductor, the probability of radiative recombination which brings about light emission is by far higher than that in an indirect transition-type semiconductor (see, K. Seeger,
Semiconductor no Butsuri Gaku
(
Ge
) (
Physics of Semiconductor
(
Last Volume
))”, 1st imp., page 507, Yoshioka Shoten (Jun. 25, 1991)). This is the reason why the light-emitting layer is preferentially composed of a direct transition-type semiconductor material. In conventional techniques, the “evaporation-preventing” layer is, however, also composed of a direct transition-type group III nitride semiconductor having a high probability of radiative recombination. In addition to light emission from the light-emitting layer composed of an indium-containing group III nitride semiconductor, light is therefore also generated from the “evaporation-preventing” layer itself. In other words, light emission of a single wavelength cannot be obtained, and this disturbs the fabrication of a light-emitting device having excellent monochromaticity.
In conventional techniques, a barrier layer provided above the “evaporation-preventing” layer is also composed of a group III nitride semiconductor intentionally doped with an impurity. For example, the barrier layer on the light-emitting layer is composed of a magnesium (Mg)-doped group III nitride semiconductor. Therefore, it has been heretofore necessary to provide a “diffusion-preventing” layer for preventing the penetration of impurity such as Mg from the barrier layer into the light-emitting layer. That is, a light-emitting device cannot be readily fabricated.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems. Specifically, the above object of the present invention has been achieved by providing the following:
(1) a p-n junction-type compound semiconductor light-emitting device comprising a substrate composed of a single crystal, a first barrier layer provided on the substrate and composed of a compound semiconductor of a first conduction type, a light-emitting layer provided on the first barrier layer and composed of an indium (In)-containing group III nitride semiconductor of a first or a second conduction type, and an evaporation-preventing layer provided on the light-emitting layer for preventing the evaporation of indium from the light-emitting layer, wherein the evaporation-preventing layer is composed of an undoped boron phosphide (BP)-base semiconductor of second conduction type;
(2) the p-n junction-type compound semiconductor light-emitting device as described in (1) above, wherein the evaporation-preventing layer almost lattice-matches with the light-emitting layer;
(3) the p-n junction-type compound semiconductor light-emitting device as described in (1) or (2) above, wherein the first barrier layer is composed of an undoped boron phosphide-base semiconductor where an impurity is not intentionally added;
(4) a p-n junction-type compound semiconductor light-emitting device comprising a substrate composed of a single crystal, a first barrier layer provided on the substrate and composed of a compound semiconductor of a first conduction type, a light-emitting layer provided on the first barrier layer and composed of an indium (In)-containing group III nitride semiconductor of a first or a second conduction type, an evaporation-preventing layer provided on the light-emitting layer for preventing the evaporation of indium from the light-emitting layer, and a second barrier layer provided on the evaporation-preventing layer and composed of a compound semiconductor of a second conduction
Duy Mai Anh
Showa Denko Kabushiki Kaisha
LandOfFree
P-n junction-type compound semiconductor light-emitting... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with P-n junction-type compound semiconductor light-emitting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and P-n junction-type compound semiconductor light-emitting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3317381