Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With heterojunction
Reexamination Certificate
1999-08-05
2003-02-25
Leke, Steven (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With heterojunction
C257S085000, C257S086000, C257S103000, C438S022000, C438S024000, C438S046000, C438S047000
Reexamination Certificate
active
06525345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor photonic device, and more particularly to semiconductor photonic devices using III-V compounds such as GaN, InGaN, GaAlN, and InGaAlN.
2. Description of the Related Art
As materials for semiconductor photonic devices such as light emitting diodes (LEDs) and laser diodes (LDs) which emit blue light or ultraviolet light, or photo diodes which detect blue light or ultraviolet light, III-V compound semiconductors represented by the general formula In
x
Ga
y
Al
z
N (where x+y+z=1, 0≦x ≦1, 0≦y≦1, and 0≦z≦1) are known. The compound semiconductors have high light emission efficiency because they are of the direct transition type, and emission wavelengths can be controlled by the indium content, and thus these compound semiconductors have been regarded as promising materials for light emitting devices.
Since it is difficult to form a large single crystal of the In
x
Ga
y
Al
z
N, in order to form a crystal film thereof, a so-called “hetero-epitaxial growth method” is used, in which a crystal film is grown on a substrate of a different material, and generally, it is grown on a C-plane sapphire substrate. However, C-plane sapphire substrates are expensive, and moreover, because of large lattice mismatching, many crystal defects at dislocation densities of 10
8
/cm
2
to 10
11
/cm
2
occur in grown crystals, and thus it is not possible to obtain quality crystal films having excellent crystallinity, which is a problem.
Consequently, in order to reduce lattice mismatching when In
x
Ga
y
Al
z
N is grown on a C-plane sapphire substrate and to obtain crystals having few defects, a method has been disclosed in which a polycrystalline or amorphous AlN buffer layer or a low temperature growth GaN buffer layer is provided on a C-plane sapphire substrate. For example, hexagonal GaN has a lattice constant in the a-axis direction (hereinafter referred to as “lattice constant a”) of 3.189 Å, and AlN has a lattice constant a of 3.1113 Å which is close to that of GaN. In accordance with the above method, since lattice mismatching between the C-plane sapphire substrate and the buffer layer is reduced and at the same time lattice mismatching between the buffer layer and In
x
Ga
y
Al
z
N is reduced, a crystal film having few defects can be obtained. However, in this method, in addition to the expensive sapphire substrate, the structure becomes complex, resulting in a further increase in cost.
Additionally, an SiC substrate which has small lattice mismatching has been investigated. However, SiC substrates are much more expensive in comparison with C-plane sapphire substrates (approximately 10 times as costly as C-plane substrates), which is disadvantageous.
SUMMARY OF THE INVENTION
The present invention can solve the aforementioned technical problems associated with the conventional devices, provide a semiconductor photonic device having a high quality In
x
Ga
y
Al
z
N thin film on an inexpensive quartz substrate.
The semiconductor photonic device comprises: a Z-cut quartz substrate; and a compound semiconductor layer represented by In
x
Ga
y
Al
z
N (where x+y+z=1, 0≦x≦1, 0≦y≦1, and 0≦z ≦1) and formed on the Z-cut quartz substrate. It is preferable that the [1000] direction, the [10{overscore (1)}0] direction, and the [11{overscore (2)}0] direction of the In
x
Ga
y
Al
z
N layer substantially correspond to the [1000] direction, the [10{overscore (1)}0] direction, and the [11{overscore (2)}0] direction of the quartz substrate, respectively. In addition, The semiconductor photonic device may further comprises a ZnO thin film or AlN thin film between the compound semiconductor layer and the Z-cut quartz substrate.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
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M.Wraback et al, Appli. Phys. Lett., vol. 74, No. 4, pp507-509, Jan. 25, 1999.
Kang Donghee
Keating & Bennett LLP
Leke Steven
Murata Manufacturing Co. Ltd.
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