Investigation of the penetration of atomic hydrogen from the gas phase into SiO2/GaAs

A comparison experiment has been performed to study the hydrogenation of GaAs samples coated with a thin film of SiO2 (5 nm) and thin-film vanadium samples in a flow of atomic hydrogen produced by a source based on a reflected arc discharge with a hollow cathode and a self-heating electrode. An increase in discharge current I results in an increase in the concentration of atomic hydrogen in the gas phase, NAH, and in a corresponding increase in the atomic hydrogen content (dose), Q(AH). dissolved in vanadium samples. For GaAs samples, the situation is different. At low discharge currents, an increase in current results in an increase in NAH and in a corresponding increase in QAH. However, beginning from some current I*, further increase in current and in NAH decreases Q(AH). This suggests that the value of Q(AH) is more dependent on the probability of the penetration of hydrogen atoms into the solid, F, than on N-AH. It has been supposed that F decreases substantially as the hydrogen atom energy decreases with increasing discharge current. Another reason for the observed phenomenon may be the formation of a near-surface diffusion barrier of immobile hydrogen molecules occupying interstitials and preventing hydrogen atoms from penetrating the bulk of the sample. (C) 2001 American Vacuum Society.