Thermal stability of Cr-Ni-Co alloy Schottky contacts on MBE -GaAs

The thermal stability of the Schottky barrier height of Cr-Ni-Co alloy Schottky contacts on an MBE n -GaAs substrate has been investigated using current-voltage ( I - V ) and capacitance-voltage ( - V ) techniques after thermal annealing for 5 min in an atmosphere at several temperatures in the 200- C range. It has been found that the value of (0.83 or 0.84 eV) remains constant up to C in the forward I - V mode. Because of the presence of an interfacial layer between the alloy contact and GaAs, an ideality factor value of 1.31 was obtained for as-deposited samples. This value decreases to 1.18 with increasing annealing temperature up to C. At annealing temperatures above C, the ideality factor n starts to increase. This has been explained in terms of the presence of different metallic-like phases produced by chemical reactions between the alloy and GaAs because of the annealing process. The ( C - V ) values obtained from the reverse-bias - V curves of the as-deposited and annealed diodes at 1 MHz are in the range 0.96-1.09 eV. The difference (0.13-0.26 eV) between ( C - V ) and the ( I - V ) is in close agreement with values reported in literature.