Papers by Keyword: Low Temperature Growth

Abstract: Polycrystalline GaN thin films were successfully grown at low temperature (250 °C) by plasma-enhanced atomic layer deposition with NH₃, N₂, N₂/H₂ gas mixture and trimethylgallium (TMG) as precusor. The growth rate, crystal structure, surface composition and the valence state of the corresponding element of the GaN thin films using different nitrogen sources were characterized and examined systematically via the spectroscopic ellipsometry, the x-ray diffractometer, the x-ray photoel-ectron spectrometer. It is showed that all the GaN thin films using different nitrogen sources were polycrystalline structure and the preffered orientation were mainly (100). The films using N₂ and N₂/H₂ gas mixture had a higher crystal quality than films using NH₃. The GPC (growth rate per cycle) would increase with the increase of the N₂ flow rate. The films using a suitable ratio of N₂/H₂ flow rate had not only a high GPC but a good crystal quality. The ratios of Ga/N element of the films using N₂/H₂ gas mixture were approximated to 1:1, it would increase with the ratio of the N₂/H₂ flow rate in the gas mixture, which is showing much effect of the ratios of N₂/H₂ flow rate on the nitrogen content of the thin films.

Abstract: The formation mechanism of a carbonized layer was investigated under low-pressure and low-temperature process conditions. The initial carbonized layer under those conditions was formed epitaxially using the silicon atoms sublimated from substrate and the carbon atoms of the gas source. This result is suggested from the consideration of pit formation mechanism at the Si/SiC interface. After the initial layer was formed, the carbonized layer grew by the diffusion process of the carbon atoms through the crystal defects in the initially formed layer. This is suggested from that the thickness of the carbonized layer increases linearly with the square root of the process time. The growth rate seemed to be determined by the concentration of carbon atoms taken into the SiC.

Abstract: The advantages of the CH3Cl carbon precursor were investigated in order to achieve good-quality homoepitaxial layers of the 4H-SiC polytype at temperatures lower than what was considered practical (or even possible) with C3H8-based growth. It was observed that the process window for good epilayer morphology becomes narrower when the growth temperature is decreased. Successful growth experiments have been conducted in this work down to a temperature of 1290-13000C, with the growth rate in excess of 2 +m/hr and a mirror-like defect-free epilayer surface morphology. Growth on a 2” substrate produced promising growth rate homogeneity. The dependence of the growth rate on SiH4 flow followed a clear exponential dependence. This trend is tentatively attributed to Si vapor condensation. Photoluminescence results suggest that the crystalline quality of the epilayers grown at 13000C is comparable to that of 17000C growth.