SCHOTTKY-BARRIER AT THE INDIUM TIN OXIDE NORMAL-GAAS INTERFACE - EFFECT OF SURFACE ARSENIC DEFICIENCY

In this paper we present the results of our studies on the Schottky barrier at the indium tin oxide (ITO)-n-GaAs interface and the effect of an arsenic-deficient GaAs surface on the barrier height. The ITO/n-GaAs junctions were prepared by depositing ITO (by a reactive thermal evaporation technique) on as-cleaned and heat-treated GaAs substrates of opening elbow-100-closing elbow orientation. The heat treatment of GaAs gave rise to an arsenic-deficient surface. The current-voltage characteristics of the Schottky diodes exhibit two current transport mechanisms: depletion region recombination and thermionic emission. The height of the Schottky barrier at the interface between ITO and as-cleaned GaAs is 0.83 +/- 0.02 eV and and that at the interface of ITO and heat-treated GaAs is 1.05 +/- 0.02 eV as evaluated using I-V and C-V methods. The results are in accordance with the defect models for Schottky barrier formation. The junctions having an enhanced barrier exhibit a photoconversion efficiency of 7.75%, the highest for any ITO/GaAs junctions reported so far.