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 Ga As samples coated with a thin film of SiO2 (5 nm) and thin-film vanadium sa mples in a flow of atomic hydrogen produced by a source based on a reflecte d arc discharge with a hollow cathode and a self-heating electrode. An incr ease 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 t he atomic hydrogen content (dose), Q(AH). dissolved in vanadium samples. Fo r GaAs samples, the situation is different. At low discharge currents, an i ncrease in current results in an increase in NAH and in a corresponding inc rease 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) i s more dependent on the probability of the penetration of hydrogen atoms in to the solid, F, than on N-AH. It has been supposed that F decreases substa ntially as the hydrogen atom energy decreases with increasing discharge cur rent. Another reason for the observed phenomenon may be the formation of a near-surface diffusion barrier of immobile hydrogen molecules occupying int erstitials and preventing hydrogen atoms from penetrating the bulk of the s ample. (C) 2001 American Vacuum Society.