The transmission spectra and the time-resolved differential reflectivity ΔR were measured in Ga1–xMnxAs, for x below 0.05 and for several excitation wavelengths. The sign of ΔR in Ga1–xMnxAs (x = 0.015 or 0.03) was negative for a photon energy larger than the band-gap at room temperature. The negative component of ΔR was explained by defect induced absorption and/or the reduction of exciton bleaching, rather than by the change in density of near band edge states associated with Mn incorporation. For Ga0.95Mn0.05As, absorption edge broadening was observed in the transmission spectra and the induced absorption effect was reduced by the screening of Mn local potential by photocarriers.

Effect of Point Defect and Mn Concentration in Time-Resolved Differential Reflection in GaMnAs. S.Kim, E.Oh, J.U.Lee, D.S.Kim, S.Lee, J.K.Furdyna: Applied Physics Letters, 2006, 88[26], 262101 (3pp)