Asymmetrical Contact Geometry to Reduce Forward-Bias Degradation in β-Ga2O3 Rectifiers

Abstract

We report a study of the effect of different Schottky contact orientations on maximum current achievable before failure and also temperature distributions in vertical geometry Ga2O3 rectifiers. Due to the strong anisotropy of thermal conductivity in Ga2O3, asymmetrical Schottky contacts are needed to provide higher current density with enhanced lateral thermal dissipation, symmetrical temperature profile and lower junction temperature at a specific diode current density compared to symmetrical contacts. Devices with rectangular contacts fabricated on (001) orientated wafers with their long axis perpendicular to the [010] crystallographic direction show much greater resistance to thermal degradation under forward bias conditions than either square contact rectifiers or those oriented with their long axis oriented perpendicular to the [100] direction. An optimized contact orientation can produce a 25% increase in maximum forward current. Practical operating conditions for Ga2O3 power devices will need to encompass all aspects of thermal management, including these geometric factors as well as active and passive cooling.