Forward bias degradation and thermal simulations of vertical geometry β-Ga2O3 Schottky rectifiers

Vertical geometry β-Ga2O3 Schottky rectifiers of various sizes were deliberately stressed at a high forward current density level until a sudden decrease of reverse bias breakdown voltage was observed. The diodes were fabricated on an Sn-doped (n = 3.6 × 1018 cm−3) (001) β-Ga2O3 single crystal substrate with a 10 μm epilayer grown by halide vapor phase epitaxy with a carrier concentration of 3.5 × 1016 cm−3. The forward bias stressing caused reverse breakdown degradation and thermally induced failure on both the Ni/Au Schottky contact and the epitaxial layer due to the low thermal conductivity of Ga2O3. The resulting temperature distributions at forward bias under different current conditions were simulated using 3D finite element analysis. The temperature profile at the surface during the rectifier turn-on period shows a strong dependence with crystalline orientation, evidenced by infrared camera measurements. The maximum junction temperature rise occurs at the center of the metal contact and is in the range of 270–350 °C.