SIGNAL STRENGTH ENHANCEMENT AND BANDWIDTH TUNING IN MOVING SPACE-CHARGE FIELD PHOTODETECTORS USING ALTERNATING BIAS FIELD

Enhancement of the photocurrent density generated by internal moving s pace charge electric fields in semi-insulating GaAs multiple quantum w ells is observed when the sample is biased with a high speed, zero-mea n square wave electric field which increases the internal space charge electric field strength. Tunability of the space charge field formati on time is also demonstrated by adjusting the amplitude of the bias si gnal. This technique can be used to enhance the sensitivity of optical doppler frequency measurements based on moving space charge field eff ects in photoconductive semiconductors. Electronic tunability of the s pace charge field formation time also adds versatility in optical powe r spectrum analysis applications. (C) 1998 American Institute of Physi cs.