An ultra-short lifetime apparatus

An apparatus is described for measuring the lifetimes of photo-injected excess carriers and surface-recombination velocities in semiconductors by the decay of photo-conductivity. The use of a high-intensity carbon arc, front-surface mirrors (one of which can be rotated at speeds up to 25000 r.p.m.), shaping slits and a relatively long optical lever (18¿20 ft) produces a light pulse that is essentially rectangular. The apparatus has been used to measure time-constants from 32 microsec to 6.6 millimicrosec. Curves of photo-conductive rise and decay are shown for indium-antimonide detector cells, a multiplier phototube and high-resistivity silicon.