Group III nitrides grown on 4H-SiC (3038) substrate by metal-organic vapor phase epitaxy
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Group III nitrides grown on 4H-SiC ( 30 3 8 ) substrate by metal-organic vapor phase epitaxy Akira Honshio1, Tsukasa Kitano1, Masataka Imura1, Yasuto Miyake1, Hideki Kasugai1, Kazuyoshi Iida1, Takeshi Kawashima1, Motoaki Iwaya1, Satoshi Kamiyama1, Hiroshi Amano1, Isamu Akasaki1, Hiroyuki Kinoshita2 and Hiromu Shiomi2 1 Faculty of Science and Technology, 21st-Century COE Program “Nano-Factory”, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan. 2
SiXON Ltd., 47 Umezutakase-cho, Ukyo-ku, Kyoto 615-8686, Japan.
ABSTRACT The heteroepitaxial growth of a GaN single crystal by metal-organic vapor phase epitaxy on a 4H-SiC ( 30 3 8 ) substrate was demonstrated. The crystallographic orientation of GaN was found to be dependent on growth pressure. When the growth pressure was 1000 hPa, the orientation of the GaN single crystal was consistent with that of the SiC substrate, where the c-plane of the GaN was single crystal tilted 54.7º from the surface plane. Then, we fabricated a violet-light-emitting diode (LED) with a GaInN multiple-quantum-well (QW) active layer grown on the GaN layer, which coherently grew on the 4H-SiC ( 30 3 8 ) substrate. The blue shift of the peak wavelength with increasing injection current of up to 100 mA was confirmed to be two times smaller than that of a conventional LED on a c-plane sapphire substrate due to a low internal polarization. INTRODUCTION Nitride semiconductors have attracted attention as one of the most promising materials for light-emitting diodes (LEDs) whose emission wavelengths range from the visible to ultraviolet regions. However, since a suitable substrate for nitrides semiconductors does not exist, the growth of high-quality GaN has been very difficult. This problem has been solved by remarkable breakthroughs in crystal growth such as the development of a low-temperature-deposited (LT-) buffer layer technique [1]. Using this technique, a high-quality GaN layer on the c-plane sapphire substrate can be obtained. Furthermore, after the formation of p-type GaN [2] and the control of conductivity of n-type GaN [3], blue and green LEDs and violet-laser diodes (LDs) were realized. Although highly efficient blue LEDs have been realized using strained GaInN multiple QWs, green or longer-wavelength LEDs still show a low emission efficiency due to the
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influences of a large piezoelectric field and a low crystalline quality. [0001]-oriented thin GaInN layers are grown coherently on a thick GaN layer, in other words, the GaInN layers are under biaxial compressive stress [4]. Moreover group III nitrides have large piezoelectric constants along the [0001] orientation [5-8]. Thus, a large piezoelectric field is induced in the above-mentioned QWs. The large piezoelectric fields in the QWs is the cause of the quantum confined stark effect (QCSE), resulting in a redshift of transition energy and a decrease in transition probability. By changing a crystallographic plane such as [ 10 1 0 ], it is expected that the magnitude of piezoelectric field can b
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