Demonstration of low resistance ohmic contacts to p-type (202̄1̄) GaN

Abstract

We demonstrate low resistance Ohmic contacts to ( semipolar p-type GaN using a thin p++–GaN contact layer. This layer was optimized by varying the V/III ratio, Cp2Mg flow, thickness, and growth rate which produced low forward voltage devices with specific contact resistivities estimated to be 4 × 10−4 Ω cm2 and 5 × 10−4 Ω cm2 for palladium contacts and indium tin oxide (ITO) contacts respectively. Forward voltages of 2.89 V and 3.47 V were obtained at 20 A cm−2 and 800 A cm−2 respectively for light emitting diodes (LEDs) emitting at 435 nm with palladium contacts. LEDs with ITO contacts had forward voltages of 2.94 V and 3.55 V at 20 A cm−2 and 800 A cm−2 respectively.