Observations of two separable photoquenching phenomena in lightly n-type bulk GaAs by optical absorption, Hall effect, and positron annihilation

We show that two different types of photoquenching effect take place under low temperature illumination of lightly n-type bulk GaAs. Both phenomena result in an increase in positron trapping at vacancies, The first associated with a decrease in EL2 absorption, is produced with light of 1.1 mu m wavelength and recovers near 100 K. While little photoquenching related to EL2 is observed after illumination close to the band edge (0.83 mu m), persistent increases in Hall voltage and positron lifetime accompanied by a decrease in near band-edge absorption are observed. These latter phenomena recover at 50 K. (C) 1996 American Institute of Physics.