Evidence of enlarged drift length in nanocrystalline porous silicon layersby time-of-flight measurements

The electron transport mechanism of nanocrystalline porous silicon (PS) has been studied for a self-supporting PS layer by a time-of-flight (TOF) meas urement. The observed TOF transient photocurrent curves are different from those of both single crystalline silicon (c-Si) and amorphous silicon (a-Si ). On the basis of the mobility-lifetime product (mu tau) deduced from TOF measurements, it is shown that the electron drift length of PS is enhanced up to 3.8 mum at 100 K and 2.6 mum at 300 K.