A study of the growth-mechanism and properties of microcrystalline silicon-germanium

Microcrystalline silicon-germanium (mu c-SiGe) films have been prepared using plasma enhanced chemical vapor deposition (CVD) of a mixture of silane, germane and hydrogen. We show that there exists an 'optimum' hydrogen-dilution to form the largest crystallite grains at each temperature. We interpret these results and the observation that under similar growth conditions, silicon crystallizes at lower dilution but has smaller grain size compared with silicon-germanium, in terms of the contrary roles of hydrogen atoms and ions in the microcrystallite formation process. An anomalous increase of the germanium content of the silicon-germanium crystallites with increasing hydrogen-dilution is traced to 'chemical transport' of the germanium-rich material deposited on the cathode. (C) 1998 Elsevier Science B.V. All rights reserved.