期刊
OPTICAL MATERIALS EXPRESS
卷 5, 期 5, 页码 1240-1249出版社
OPTICAL SOC AMER
DOI: 10.1364/OME.5.001240
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资金
- Ministry of Economic Affairs (Taiwan, R.O.C.) [102-E0605]
- National Science Council (Taiwan, R.O.C.) [102-2221-E-005-072-MY3, 102-2811-E-005-004]
Monoclinic gallium oxide thin films were grown on (0001) sapphire at various substrate temperatures ranging from 400 to 1000 degrees C by pulsed laser deposition using a KrF excimer laser. The structural, optical and compositional properties of the films were analyzed by using x-ray diffraction, transmission electron microscopy, optical transmittance, and Rutherford backscattering spectroscopy. As the substrate temperature was increased to 800 degrees C, the gallium oxide film possesses single crystalline phase with a preferred growth orientation of (-201) plane and higher crystal quality than those at the other temperatures. Optical transmittance measurements reveal the films grown at 600-1000 degrees C exhibit a clear absorption edge at the deep ultraviolet region around 250 nm wavelength. Based on the results of Rutherford backscattering spectroscopy, the O/Ga ratio of gallium oxide film increased gradually with increasing substrate temperature. When the substrate temperature was raised to 800-1000 degrees C, the film composition was close to the formation of Ga2O3, indicating the O vacancies and defects were reduced. Furthermore, the films grown at 600 and 800 degrees C were chosen to fabricate solar-blind metal-semiconductor-metal photodetectors. At an applied bias of 5 V, the photodetector prepared with 800 degrees C-grown film has a lower dark current of 1.2 x 10(-11) A and a higher responsivity of 0.903 A/W (at a wavelength of 250 nm) than those with 600 degrees C-grown films. The better device performance is ascribed to the higher crystal quality and fewer O vacancies in the 800 degrees C-grown film. Moreover, the results indicate the gallium oxide films presented in this study have high potential for deep ultraviolet photodetector applications. (C) 2015 Optical Society of America
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