NONLINEAR-OPTICAL RESPONSE OF AS-ION IMPLANTED GAAS STUDIED USING TIME-RESOLVED REFLECTIVITY()

The transient reflectivity response of GaAs with a 2% excess As concen tration (GaAs:As), prepared by As+ ion implantation, has been measured at photon energies near the band gap. Results are compared with simil ar measurements on implanted GaAs with a 0.01% excess As concentration , and unimplanted GaAs. For GaAs:As, the transient refractive index ch ange Delta n, is larger than, but of the opposite sign to that of unim planted GaAs. The measured carrier lifetime of 1+/-0.1 ps is identical to that of low-temperature GaAs. The wavelength dependence of Delta n indicates the presence of an induced absorption peak at photon energi es near the band gap, which is attributed to band-gap renormalization. (C) 1996 American Institute of Physics.