Optical and chemical analysis of the Ag In_0.53Ga_0.47As interface formed at low temperature

The barrier height is found to increase from 0.25 to 0.60 eV for Schottky contacts on n-InGaAs using deposition of Ag on a substrate cooled to 77 K (LT). Surface analysis leads to an interface model for the LT diode in which there are oxide compounds of In:O and As:O between the metal and semiconductor, leading to behavior as a metal-insulator-semiconductor diode. The metal film deposited at LT has a finer and more uniform structure, as revealed by scanning electron microscopy and in situ metal layer resistance measurement. This increased uniformity is an additional reason for the barrier height improvement. In contrast, the diodes formed at room temperature exhibit poorer performance due to an unpassivated surface and non-uniform metal coverage on a microscopic level.