Eects of thin oxide in metal–semiconductor and metal– insulator–semiconductor epi-GaAs Schottky diodes

The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of metal–insulator–semiconductor (MIS) GaAs Schottky diodes are investigated and compared with metal–semiconductor (MS) diodes. The MIS diode showed nonideal behavior of I–V characteristics with an ideality factor of 1.17 and a barrier height of 0.97 eV. The energy distribution of interface states density was determined from the forward bias I–V characteristics by taking into account the bias dependence of the eective barrier height, though it is small. The reduction in the saturation current in the MIS case is caused by a thin oxide layer and is due to the combination of increased barrier height and a decrease in the Richardson constant. The carrier concentration anomaly observed between the MIS and MS diodes measured from reverse bias C–V measurements is explained via oxide (b-Ga2O3) traps due to the Ga-vacancy by deep level transien