DIFFUSION AND ELECTRONIC STATES OF HYDROGEN IN N-TYPE GAAS AND N-TYPE GA1-XALXAS

Deuterium diffusion experiments have been performed in silicon-doped GaAs and Ga1-xAlxAs (x less-than-or-equal-to 0.30). In GaAs, the hydrogen diffusion profile closely fits a complementary error function. In Ga1-xAlxAs alloys with x greater-than-or-equal-to 0.055, the profiles present a plateau followed by a sharp decrease. To interpret this difference we propose that in n-type GaAs:Si and Ga1-xAlxAs:Si, hydrogen behaves as a deep acceptor with a level H-/0 slightly resonant in the conduction band of GaAs and emerging as a localized state for x > 0.07 as the band-gap energy increases. Then, for x > 0.07, the H- species become dominant and are trapped on the positively charged donors during diffusion.