A COMPARISON OF THE HYDROGENATED AMORPHOUS SI SCHOTTKY-BARRIER AND THE HYDROGENATED AMORPHOUS SI P-I-N DARK FORWARD-BIAS CURRENT DENSITY-VOLTAGE CHARACTERISTICS

Using detailed computer simulations we explore the origin of the curre nt density differences experimentally observed in the dark current den sity-voltage (J-V) characteristics of hydrogenated amorphous Si (a-Si: H) Schottky barriers and a-Si:H p-i-n homojunctions. Schottky barrier devices show higher dark current densities at low forward biases and p -i-n devices show higher current densities at high forward biases. Com puter modelling shows that at low forward voltages the transport mecha nism limiting the total current density is drift diffusion over the ba rrier in Schottky barriers and recombination through localized states in p-i-n diodes. On the other hand at high forward bias voltages the l imiting transport mechanism is electron space-charge-limited current i n both devices. We found that the non-blocking nature of the p-i-n fro nt contact is the ultimate cause for the higher current densities obse rved experimentally in a-Si:H p-i-n structures at high forward biases. In this paper we also compare the illuminated forward-bias J-V charac teristics of both devices when they are forward biased past the flat-b and condition and we show fits to experimental results for both dark a nd illuminated forward-bias J-V characteristics for devices with two d ifferent thicknesses of the intrinsic layers.