Decay Times of Impulse Surface Photovoltages in p-Type Silicon Wafers

The fixed oxide charge in a p-type silicon wafer forms a depletion layer composing a capacitor at the wafer surface, and an impulse surface photovoltage (iSPV) appears across the depletion layer when photocarriers excited by an impulse photon beam are stored in the capacitor. The iSPV eventually disappears when excess electrons and holes in the capacitor recombine with each other through conductive paths owing to crystal imperfection and/or interface traps. Two decay times of 7.3 and 8.4 ms have been observed for the original mirror-polished and additionally dry-etched surfaces of a sample wafer of 75 mm diameter; the longer decay time suggests higher crystal quality.