Picosecond photoconductive response of polycrystalline silicon thin films

Using autocorrelation measurement, we have studied the picosecond photoconductivity of as-deposited, fine-grain polycrystalline silicon thin films. A strong correlation between photoconductive decay time and polycrystalline silicon deposition temperature has been observed. The fastest autocorrelated photoconductive response is 9 ps full width at half maximum, and is obtained from a polycrystalline silicon sample deposited at 590 °C. We estimated the carrier mobility from the peak autocorrelated current, as well as from the average photocurrent of a single gap. These two values show a large difference for samples deposited at relatively high temperatures, which can be explained by imperfect metal-semiconductor ohmic contacts.