Semiconductor light-emitting device

Details Semiconductor light-emitting device Semiconductor light-emitting device

1997-09-08

2001-02-13

Jackson, Jr., Jerome (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Incoherent light emitter structure

With particular semiconductor material

C257S097000, C257S096000

Reexamination Certificate

active

06188087

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor light-emitting device. This semiconductor light-emitting device can be utilized as a light-emitting diode, a laser diode, or the like.
2. Description of the Conventional Art
Light-emitting devices using compound semiconductors cover visible short wavelength regions. Among other light-emitting diodes, nitride III semiconductors have attracted attention in recent years because these semiconductors are direct transition semiconductors, so that they exhibit high light-emitting efficiency, and because these semiconductors emit blue light, which is one of the three primary colors.
When the light-emitting layer is formed of In
X
Ga
1−X
N, it has heretofore been considered that a relation such as shown by the dashed line in
FIG. 1
exists between the indium mole fraction X and the photon energy (see “Journal of applied physics”, Vol. 46, No. 8, August 1975, pp. 3432-3437 and “Microelectronics Journal”, 25 (1994), pp. 651-659). The photon energy of the wavelength &lgr; of blue light (470 nm) is almost 2.64 eV, and the photon energy of the wavelength &lgr; of green light (520 nm) is almost 2.38 eV. Therefore, according to the conventionally proposed relation, blue emission is obtained by setting the indium mole fraction X to approximately 0.26 and green emission is obtained by setting the indium mole fraction X to approximately 0.67 if no impurities are to be added.
As a result of a continued study on the light-emitting layer formed of In
X
Ga
1−X
N, the inventors realized that the conventionally proposed relationship shown by the dashed line in
FIG. 1
could not be applied without modification if such a light-emitting layer is to be formed on a sapphire substrate.
SUMMARY OF THE INVENTION
To overcome the aforementioned problem, the inventors further studied the relationship between the indium mole fraction X and the photon energy in a light-emitting layer formed of In
X
Ga
1−X
N on a sapphire substrate. As a result, a relationship shown by the solid line in
FIG. 1
was found. When converted into a relationship between a wavelength &lgr; and the indium mole fraction X, this relationship can be given as follows.
&lgr; (
nm
)=1239.8/
Eg
(
eV
)  (1)
Eg=
3.4*(1−
X
)+1.95*
X−
4.26*
X*
(1−
X
)  (2)
According to the above equations (1) and (2), a ray of light having a peak wavelength ranging from 460 to 480 nm is emitted when the indium mole fraction X is set to 0.14 to 0.16. As a result, when the indium mole fraction X in a light-emitting layer formed of In
X
Ga
1−X
N on a sapphire substrate was set to 0.13 to 0.18, it was found that blue light, i.e., blue light as visually observed by people, was emitted from such a light-emitting layer.
Further, according to the above equations (1) and (2), a ray of light having a peak wavelength ranging from 510 to 530 nm is emitted when the indium mole fraction X is set to 0.20 to 0.23. As a result, when the indium mole fraction X in a light-emitting layer formed of In
X
Ga
1−X
N on a sapphire substrate was set to 0.19 to 0.26, it was found that green light, i.e., green light as visually observed by people, was emitted from such light-emitting layer.
The solid line in
FIG. 1
that shows the newly discovered relationship is characterized by a line more sharply inclined than the dashed line in
FIG. 1
, which shows the conventionally proposed relationship. A conceivable reason therefore is that since the lattice constant of a semiconductor constituting the light-emitting layer is different from that of the sapphire substrate, the light-emitting layer is distorted, and as a result, the photon energy is decreased, i.e., the wavelength is shifted toward long wavelengths even if the indium mole fractions are the same.
The relationships shown in
FIG. 1
illustrate cases where light-emitting layers are formed of In
X
Ga
1−X
N with no intentional impurities contained.
Of course, impurities can be doped into a compound semiconductor constituting a light-emitting layer. When impurities are doped into a light-emitting layer, the wavelength is shifted toward long wavelengths even if the indium mole fraction is the same. On the other hand, if the light-emitting layer contains a quantum well layer, the wavelength is shifted toward short wavelengths due to quantum effects.
It may be noted that the data shown by the solid line in
FIG. 1
were obtained as follows.
A 2 &mgr;m-thick GaN layer was formed on a surface a of a disc-like 100 &mgr;m-thick sapphire substrate by means of a metal organic vapor phase epitaxial growth method (hereinafter abbreviated as the “MOVPE method”), and a 20 nm-thick In
X
Ga
1−X
N layer was formed thereon similarly by means of the MOVPE method.
A pulse laser was irradiated (at an excitation strength of 200 kW/cm
2
) onto the In
X
Ga
1−X
N layer at room temperature. Then, the wavelength &lgr; of a ray of light emitted from the In
X
Ga
1−X
N layer was measured. The photon energy Eg was calculated from the peak wavelength &lgr; of such ray of light. It may be noted that such a relationship as &lgr;=1239.8/Eg is established between the wavelength &lgr; and the photon energy Eg (eV).
The indium mole fraction was calculated by means of an AES (Auger electron spectroscopy) method.


REFERENCES:
patent: 5466950 (1995-11-01), Sugawara et al.
patent: 5502316 (1996-03-01), Kish et al.
patent: 5592501 (1997-01-01), Edmond et al.
patent: 5641582 (1997-06-01), Nire et al.
patent: 5656823 (1997-08-01), Kruangam
patent: 5760945 (1998-06-01), Coleman
patent: 5877558 (1999-03-01), Nakamura et al.
patent: 5929466 (1999-07-01), Ohba
“P-GaN/N—InGaN/N—GaN Double—Heterostructure Blue-Light-Emitting Diodes,” Jpn. J. Appl. Phys., Nakamura et al., vol. 32, pp. L8-L11, 1993.
Shuji Nakamura; Growth of InxGa(1-x)N Compound Semiconductors and High-Power InGaN/AIGaN Double Heterostructure Violet-Light-Emitting Diodes; Microelectronics Journal, vol. 25; (1994), pp. 651-659.
Kozo Osamura, et al.; Preparation and Optical Properties of Ga1-xInxN Thin Films; Journal of Applied Physics; vol. 46, No. 8; Aug. 1975; pp. 3432-3437.

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