Picosecond relaxation mechanisms in highly excited GaInAsP

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Abstract
We have investigated the relaxation dynamics of highly excited GaxIn1−xAsyP1−y/InP with 5-ps resolution using a mode-locked 1.054-μm Nd:glass laser. Two samples with band gaps of 1.49 and 1.24 μm were studied at room temperature by the time-resolved nonlinear transmission and transient grating techniques. At excited carrier densities ≳5×1018 cm−3 carrier relaxation times as short as 6 ps have been measured. The results are consistent with ultrafast decay by stimulated radiative recombination, and time-integrated luminescence measurements support this interpretation. We find no evidence for plasma expansion. At lower densities the carrier relaxation is determined by Auger and bimolecular recombination, and longer decay constants in the range 100–500 ps are measured.