Studies on metal/n-GaAs Schottky barrier diodes: The effects of temperature and carrier concentrations

Abstract

Metal/Semiconductor Schottky diodes were fabricated to study the effect of temperature and carrier concentrations on diode parameters, such as ideality factor and barrier heights. The diodes were formed on the epitaxial layers of metal organic chemical vapor deposition (MOCVD) grown n-GaAs with metals such as Al, Pd, and Zn–Pd deposited onto n-GaAs by thermal evaporation technique. Trimethyl gallium and AsH3 were used as Ga and As precursors, respectively, to grow GaAs on semi-insulating GaAs substrates at 600 °C and H2S was used for n-type doping in a horizontal reactor atmospheric pressure MOCVD system. The Schottky diodes were characterized by forward bias current-voltage measurements in the temperature range 130–300 K and capacitance-voltage measurement at room temperature and diode parameters such as ideality factor and barrier height have been evaluated. It is found that the Schottky barrier height decreases with decrease in temperature while the ideality factor increases. It is also observed that the barrier height increases linearly with the applied forward bias voltage and the rate of change of barrier height with voltage increases for higher carrier concentration of the semiconductor. The carrier concentration of n-GaAs was chosen in the regime 1×1016–8.2×1016 cm−3 so that the depletion region extends inside the semiconductor and the diode can be used as a III–V photovoltaic device.