Abstract

Low-temperature grown GaAs has found various applications in optoelectronics [1] and ultrashort laser physics [2] due to the short lifetime of carriers in the bands. This is the result of arsenic antisite deep levels [3] whose concentration increases with decreasing growth temperature T_gr Here we demonstrate by 100-fs pump-probe experiments that after band-to-band excitation the rapid trapping of carriers in deep levels is followed by slow recombination of trapped carriers in samples with T_gr <300 °C. As a consequence, an excess carrier population can build up in the deep levels, which can lead to an induced absorption signal [4]. We show that at high excitation densities the deep levels can be saturated. As a result of the saturation, carriers remain in the bands leading to bleaching signals which last for more than 100 ps. Our data indicate that the recombination of trapped carriers is faster in samples grown at higher temperatures.

© 1996 IEEE