Data acquired from our cryogenic wafer prober is compared to data acquired utilizing a standard 68-pin dewar. ROIC noise, transimpedance, transimpedance linearity, slew rate, data valid time, operating speed, and dynamic range test data are presented. The multiplexer is very flexible and can be used in various operating modes. Our studies suggest that dislocations which originate in the InP substrate are the major cause of popcorn noise. This noise can be significantly reduced or completely eliminated by reducing the reverse bias of the photodiodes from 5 V to 2 V or less.
Crystal defects seem to cause the popcorn noise when the diode is substantially depleted.