Interactions between H2 and N2 plasmas and a GaAs(100) surface: Chemical and electronic properties

Abstract

The existence and possible origin of surface states on GaAs surface exposed to an N₂ plasma have been studied on surfaces cleaned by H₂ plasma in a UHV system. The H₂ plasma is shown to be very effective in reducing the C and N concentrations at the surface and to a lesser extent, the O concentration. A subsequent heating around 530 °C removes the remaining oxygen and gives a clean surface. The interaction of these clean surfaces with an N₂ plasma shows a two‐time constant behavior: (i) a rapid (5 s for our experimental conditions) dielectric (nitride) formation associated with an increase of the work function; (ii) a slow (∼100 s) decrease of the surface photovoltage and of As concentration at the surface. Comparison of n‐ and p‐type samples seems to indicate that this is due to a reduction of the band bending depending on the final As concentration.