Solar Energy Materials and Solar Cells 31 (1993) 215-226 North-Holland Solar Energy Materials and Solar Cells Effect of power and pressure on the properties of hydrogenated amorphous silicon films prepared by DC glow discharge Tanay Seth, P.N. Dixit, O.S. Panwar and R. Bhattacharyya Thin Film and Amorphous Materials Group, National Physical Laboratory, Dr. K.S, Krishnan Road, New Delhi 110 012, India Received 1 February 1993 Hydrogenated amorphous silicon films prepared at different rates of deposition up to 18 ,~ s-l, on the anode of a DC glow discharge reactor have been studied for their optoelectronic properties. In this system, use of earthed shield to confine the plasma has been utilised and one does not need to use any "grid", as has previously been found necessary to deposit device quality films on insulating substrates. Films are grown at three pressure regimes, i.e. 0.3, 0.5 and 1.0 Torr without any dilution of silane and, it is found, that the best quality films at high rates can only be obtained at = 0.5 Tort silane pressure in this system (~rph/~r D ~ 105 and E 0 values 54.8 meV at 13 A s-l). 1. Introduction The fact that even almost after two decades of the first report of glow discharge produced amorphous silicon films, basic plasma CVD processes continue to be studied seriously and, ever so often, new interesting results surface, is not surpris- ing since plasma processes are basically nonintuitive. It is only recently that a degree of success has been achieved in modeling a laboratory plasma and some very sophisticated experiments undertaken to discern the subtilities of the glow discharge processing of the material [1]. Similarly, high rate deposition of a-Si : H, involving glow discharge techniques, in the meanwhile, has assumed great techno- logical importance in view of the high values of thickness of such material that one requires to fabricate newer electrophotographic layers, radiation and charged particle detectors, and for the mass production of solar cells that has a bearing on the cost of producing solar panels, etc. Thicknesses of a-Si : H films in many cases easily run into tens of microns. Some of the techniques which have since been evolved to achieve such high deposition rate are use of cathode shields, high frequencies discharges (RF > 70 MHz, microwave 2.45 GHz with ECR), RF tuning of substrate electrode to pull the glowing plasma to the anode and remote plasma CVD, etc. [2-5]. These techniques have been attempted with Sill 4 and higher silanes with or without dilution with H z, He, etc. 0927-0248/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved