Temperature-Dependent Electrical Characteristics of beta-Ga2O3 Diodes with W Schottky Contacts up to 500 degrees C

The development of thermally stable contacts capable of high temperature operation are necessary for Ga2O3 high power rectifiers. We have measured the electrical characteristics of sputter-deposited W Schottky contacts with Au overlayers for reducing sheet resistance on n-type Ga2O3 before and after device operation up to 500 degrees C. Assuming thermionic emission is dominant, the extracted barrier height decreases with measurement temperature from 0.97 eV (25 degrees C) to 0.39 eV (500 degrees C) while showing little change from its initial value of 0.97 eV after cooling down from each respective operation temperature. The room temperature value is comparable to that obtained by determining the energy difference between binding energy of the Ga 3d core level and the valence band of the Ga2O3 when W is present, 0.80 +/- 0.2 eV in this case. The Richardson constant was 54.05 A.cm(-2).K-2 for W and the effective Schottky barrier height at zero bias (e Phi(b0)) was 0.92 eV from temperature-dependent current-voltage characteristics. The temperature coefficient for reverse breakdown voltage was 0.16 V/K for W/Au and 0.12 V/K for Ni/Au. TheW-based contacts are more thermally stable than conventional Ni-based Schottkies on Ga2O3 but do show evidence of Ga migration through the contact after 500 degrees C device operation. (C) The Author(s) 2018. Published by ECS.