RESPONSE-TIME MEASUREMENTS IN MICROCRYSTALLINE SILICON

The response time, tau(R), measured by the small-signal photocurrent d ecay in hydrogenated microcrystalline silicon films (mu c-Si:H), which were prepared by three different deposition techniques, reaches value s of about 20 mu s for the initial decay and more than 100 mu s at lon ger times whereas it is typically 1 mu s in hydrogenated amorphous sil icon. We have correlated tau(R) with the dark conductivity activation energy since it is related to the Fermi level position. Quite similar to n-type amorphous films, tau(R) increases in mu c-Si:H films when th e Fermi level moves towards the conduction band edge. We studied this behavior numerically and discuss to what extent the analysis applies t o both amorphous and microcrystalline films.