Picosecond recombination of charged carriers in GaAs

The recombination kinetics of charged carriers in GaAs have been investigated on a picosecond time scale. A pump-probe technique was used to measure reflectivity changes as a function of time up to 900 ps. Initially, (1.2±0.2)×1020 carriers/cm3 were excited into the conduction band. The decay curve indicated dominance of a three-body (Auger) recombination process up to about 120 ps, with two-body recombination processes dominating after 120 ps, the switch occurring at a carrier concentration of (5±2)×1019 carriers/cm3. Values for the Auger recombination coefficient and the two-body recombination coefficient were determined to be (7±4)×10−31 cm6 s−1 and (3.4±1.7)×10−11 cm3 s−1, respectively. The change in reflectance was observed to have essentially returned to zero within 900 ps.