Nonlinear optical response of As+-ion implanted GaAs studied using time resolved reflectivity

Abstract

The transient reflectivity response of GaAs with a 2% excess As concentration (GaAs:As), prepared by As+ ion implantation, has been measured at photon energies near the band gap. Results are compared with similar measurements on implanted GaAs with a 0.01% excess As concentration, and unimplanted GaAs. For GaAs:As, the transient refractive index change Δn, is larger than, but of the opposite sign to that of unimplanted GaAs. The measured carrier lifetime of 1±0.1 ps is identical to that of low-temperature GaAs. The wavelength dependence of Δn indicates the presence of an induced absorption peak at photon energies near the band gap, which is attributed to band-gap renormalization.