TRANSIENT PHOTOCONDUCTIVITY IN A WIDE ALGAAS BARRIER

The transient photocurrent flowing over a wide undoped AlGaAs barrier has been investigated as a function of bias voltage, voltage polarity, laser intensity and sample temperature. Excitation was by pulses of l ength 100 ps from a Nd:YAG laser. The radiation, which uniformly illum inated the top surface of the mesa, could produce excess carrier densi ties of the order of 1 X 10(19) cm-3. The time constant of the decay f or zero bias was 4 ns at 100 K. It was independent of laser intensity, which suggests that the lifetime was determined by radiative recombin ation in the contact regions. A trap-limited hole mobility of 2 cm2 V- 1 s-1 was deduced from the low-field data.