More Stable Low Gap a-Si:H Layers Deposited by PECVD at Moderately High Temperature with Hydrogen Dilution

In the present work, several series with variation of deposition parameters such as hydrogen dilution ratio, VHF-power and plasma excitation frequency fexc have been extensively analyzed. Compared with conventional' more-stable layers obtained at 200-250 °C and high H2 dilution ratios of about 10, it was observed that electrical transport properties after light-induced degradation of layers deposited at moderately high' temperatures (300-350 °C) are equivalent but required lower H2 dilution ratios (between 2 and 4). As a consequence, the deposition rate of more stable layers obtained at moderately high temperatures is increased by a factor of 2. Moreover, optical gaps of a-Si:H deposited at 300-350 °C are significantly lower (by approx. 10 meV); furthermore, they decrease with fexc.