Influence of a thin intrinsic a-Si:H layer on the I–V characteristics of a-Si:H/c-Si diodes made by hot-wire CVD

P-type amorphous silicon was deposited on crystalline n-type silicon substrates to obtain hetero-junction diodes. Additionally, a thin intrinsic amorphous silicon layer was inserted between both the p-type film and the n-type substrate to study its passivation effect on the c-Si surface. We studied the influence of the quality of the amorphous films upon the performance of the hetero-junction diodes. In particular, the diode ideality factor and the saturation current density were determined by measuring the current-voltage characteristics in dark conditions. The amorphous films were obtained by the hot wire chemical vapor deposition (HWCVD) technique, using a tungsten filament and SiH₄, H₂ and B₂H₆, where the deposition parameters such as gas flow, substrate temperature and filament temperature were varied. It is be shown that the presence of the intrinsic layer is fundamental for making good diodes, since devices made without this film cause the diodes to have high saturation current density and ideality factor (3 × 10^-5 A/cm², n > 8) as compared to diodes with a good intrinsic layer (5 × 10^-9 A/cm², n = 1.4). The results obtained are encouraging, but the quality of the intrinsic films still should be improved for applying them to HIT (Hetero-junction with Intrinsic Thin layer) solar cells.