SCHOTTKY DIODE PROPERTIES AND THE PHOTOVOLTAIC BEHAVIOR OF INDIUM TIN OXIDE (ITO)/N-GAAS JUNCTIONS - EFFECT OF ARSENIC DEFICIENT GAAS SURFACE

Studies on the Schottky barrier properties of ITO/n-GaAs junctions and their photovoltaic behaviour are reported. The junctions were prepared by depositing ITO by reactive thermal evaporation technique on as-cleaned and heat-treated GaAs substrates of (100) orientation. The barrier height of the Schottky diodes prepared on as-cleaned GaAs is 0.83+or-0.02 eV as measured by I-V and C-V methods, and is nearly the same as in the case of many other metal/n-GaAs interfaces. Heat-treated GaAs having arsenic deficient surfaces produced a larger barrier height ( approximately=1.05 eV). As a result of the barrier height enhancement, the ITO/n-GaAs junctions exhibited an increase in the open circuit voltage and photoconversion efficiency from 435 mV and 4.94% to 585 mV and 7.75%, respectively. The efficiency of 7.75% is perhaps the highest for any ITO/GaAs junctions reported so far. The results are discussed on the basis of the defect models for Schottky barrier formation.