In the present work, several series with variation of deposition parameters such as hydrogen dilution ratio, VHF-power and plasma excitation frequency f(exc) have been extensively analyzed. Compared with "conventional" more-stable layers obtained at 200-250 degreesC and high H-2 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 degreesC) are equivalent but required lower H-2 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 degreesC are significantly lower (by approx. 10 meV); furthermore, they decrease with f(exc). (C) 2001 Elsevier Science B.V. All rights reserved.