PASSIVATION OF SHALLOW AND DEEP LEVELS BY HYDROGEN PLASMA EXPOSURE INALGAAS GROWN BY MOLECULAR-BEAM EPITAXY

We report on the effects of exposure to a hydrogen plasma (hydrogenati on) and of thermal annealing (dehydrogenation) on shallow and deep lev els in direct-gap AlGaAs:Si grown by molecular beam epitaxy. Photolumi nescence (PL) experiments show that hydrogenation results in the passi vation of shallow levels, thus confirming the data of capacitance-volt age measurements, while deep-level transient spectroscopy shows that M E5, ME6 and DX centers are passivated by hydrogenation. Dehydrogenatio n at 420 degrees C results in an almost complete recovery of the free electron concentration, and restores, to a significant extent, only th e DX center. The study of samples grown at different temperatures show s that the significant increase of the PL efficiency after hydrogenati on and its decrease after dehydrogenation are consistent with the pass ivation of the ME5 and ME6 levels and with their partial reactivation, respectively.