Picosecond absorption dynamics of photoexcited InGaP epitaxial films

The absorption recovery of a photoexcited InGaP epitaxial film 0.4 μm thick was investigated using the pump-probe laser technique and found to have a time constant of 55 ps at room temperature. Measurements done in the temperature range of 300–50 K show the decay of the photoexcited carrier distribution to be dominated by ambipolar diffusion and surface recombination. The measured absorption recovery time constant corresponds to an ambipolar diffusion coefficient D≳2.8 cm2/s and a surface recombination velocity of S≳4×105 cm/s at room temperature.