ULTRAFAST HIGH-INTENSITY NONLINEAR ABSORPTION DYNAMICS IN LOW-TEMPERATURE-GROWN GALLIUM-ARSENIDE

We study carrier dynamics in GaAs thin films grown by molecular beam e pitaxy at 250, 300, and 350 degrees C by differential transmission exp eriments at various carrier excitation densities. The differential tra nsmission shows that carrier trapping in point defects is much faster than the recombination of the trapped carriers. As a consequence, the defect states can be saturated at high carrier densities. if the growt h temperature is decreased, the initial trapping becomes faster while the subsequent recombination of the trapped carriers becomes slower. W e show that this is due to the growth temperature dependent defect den sities. (C) 1996 American Institute of Physics.