Fabrication and Properties of AlGaN/GaInN Double Heterostructure Grown on 6H-SiC(0001) Si
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ABSTRACT AIGaN/GaInN double heterostructures (DH) were fabricated by metalorganic vapor phase epitaxy on the (0001)si 6H-SiC substrate. A cleaved edge shows a very flat surface with roughness on the order of one monolayer. Stimulated emission and laser action from the UV to blue region was observed by optical pumping at room temperature (RT). The threshold power density was 27KW/cm 2 which is smaller than that of the same structure grown on a sapphire (0001) substrate by a factor of four. A AIGaN/GalnN DH UV light emitting diode, using undoped GaInN is fabricated. The power efficiency and spectra width of this LED is comparable or superior to that of an LED having the same structure but grown on sapphire.
INTRODUCTION Special attention is paid to the group III nitrides because of their large and direct bandgaps ranging from 1.9eV to 6.2eV. Applications as new light sources and detectors in the short wavelength region are expected. Moreover, they are promising for application as high-power microwave devices because they also have high-thermal conductivity and large electron saturation velocity. Significant pioneering work has been done in the early 1970s by Maruska and Tietjen [1], Pankove [2], and Maruska et al. [3] on the crystal growth, the characterization of basic properties, and the fabrication of the first MIS-type blue light emitting diode (LED) of GaN. However, the difficulty in growing high-quality films due to the lack of substrate materials with lattice constant and thermal expansion coefficients close to those of group I1I nitrides, and the difficulty in obtaining p-type films have long prevented their use. In 1986, we succeeded in growing high-quality GaN on sapphire substrate by metalorganic vapor phase epitaxy (MOVPE) using a low-temperature deposited AIN buffer layer [4]. Lowtemperature deposited GaN buffer layer also showed similar effect [5]. In 1989, p-type GaN was realized for the first time by low-energy electron beam irradiation (LEEBI) treatment of MOVPE-grown Mg-doped highly resistive film [6]. P-type GaN has also been obtained by thermal treatment in hydrogen-free atmosphere [7]. Hydrogen passivation of the doped Mg is proposed [7-9]. Based upon the above mentioned findings together with the use of alloys to control the emission wavelength [10], bright blue light emitting diodes (LED) composed of group III nitrides have become commercially available [11-14]. One of the next steps may be the realization of laser diodes (LD). Dingle et al. reported, for the first time, stimulated emission (SE) and laser action by optical pumping from a GaN needle crystal at 4.2K with the threshold power density (Pth) of 0.3MW/cm 2 [15]. Cingolani et 869
Mat. Res. Soc. Symp. Proc. Vol. 395 0 1996 Materials Research Society
al. reported the SE from a GaN needle crystal and epitaxial layers at up to 120K [16], with a Pth of about 3MW/cm 2. They emphasized the origin of the SE is electron hole plasma (EHP). Some of the present authors reported the first room temperature SE from2 epitaxial GaN film grown on sa
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