Photocurrent in Microcrystalline Hydrogenated Silicon P-I-N Devices

Abstract

ABSTRACTThe photocurrent delivered by microcrystalline hydrogenated silicon p-i-n devices and the spectral response are analysed under different applied bias voltage. The spectral response is extended far beyond 900 nm. Under reverse bias the spectral response is high and essentially unchanged while under increasing forward bias it decreases continuously. For forward bias higher than the open circuit voltage, the usual reversal of the spectral response is not observed and the photocurrent remains negative and almost independent of the bias voltage. A heterojunction model based on the presence of additional local electric fields near the grain boundaries is presented to explain this behaviour. Those fields lead to a strong increase of the recombination at the grain boundaries decreasing the contribution from the photogenerated carriers for the secondary photocurrent. Reverse bias restores the electric field at the interfaces minimizing the influence of the local barriers.