Effect of Hydrogen Plasma Treatment on n-InP Surfaces

Surfaces of n-InP treated with remote hydrogen plasma have been analyzed in terms of X-ray photoelectron spectroscopy (XPS), Kelvin probe, current-voltage characteristics of Schottky barrier junctions and isothermal capacitance transient spectroscopy (ICTS). It is confirmed by XPS analysis that the native oxide is removed from the InP surface by the \H2-plasma treatment. Schottky junctions formed byin situevaporation of various metals immediately after the remote \H2-plasma exposure show that the barrier height is pinned at about 0.5 eV, irrespective of Schottky metal. This value is somewhat higher than the barrier height of 0.4 eV for untreated surfaces. It is observed by Kelvin probe measurement that the Fermi level shifts to an energy around 0.53 eV below the conduction band edge upon \H2-plasma treatment from 0.39 eV for an untreated surface. Furthermore, a deep trap level with the activation energy of 0.51 eV below the conduction band edge was detected for samples treated with \H2 plasma by ICTS measurement. The pinned behavior of the Schottky barrier height is speculated to be related to the trap level generated by \H2-plasma treatment.