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

Abstract

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), QAH, 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 QAH. This suggests that the value of QAH is more dependent on the probability of the penetration of hydrogen atoms into the solid, F, than on NAH. 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.

<title>Modeling atomic hydrogen diffusion in GaAs</title>

“…At that active storage of molecular hydrogen and its spread in depth crystal is continued.With growth off0 and decrease of hydrogenation temperature duration of each stage becomes shortened. Paper [7] reports that during fixed hydrogenation time an increase in density of penetrating atomic flow results, first, in proportional growth of hydrogen doze introduced in crystal, then the increase of doze becomes slow leading to the situation when further increase in penetrating flow does not lead to growth of hydrogen doze in crystal. The effect is connected with formation of surface molecular barrier preventing to hydrogen atoms penetration in crystal and their further diffusion.…”

“…The effect is connected with formation of surface molecular barrier preventing to hydrogen atoms penetration in crystal and their further diffusion. During this work, owing to improving calculation algorithm, we have managed to obtain solutions of equation system (1) for penetrating flows by four orders ofmagnitude higher than those used in [7].…”