Ohmic Cathode Electrode on the Backside ofm-Plane and (2021) Bulk GaN Substrates for Optical Device Applications

Cathode electrodes on the backside of n-type nonpolar m-plane (1100) and semipolar (2021) GaN substrates after thinning were investigated. For m-plane, Al deposition after inductively coupled plasma exposure resulted in ohmic characteristics with a specific contact resistivity of 1.6 ×10-4 Ω cm2 without annealing, where the sub-micron-order pillar-like micromasking were considered to contribute to the ohmic contact. For (2021), ohmic characteristics with a specific contact resistivity of 6.9 ×10-5 Ω cm2 was confirmed with Ti/Al electrode after annealing at 500 °C. Such electrodes could improve wall-plug efficiencies of nonpolar and semipolar GaN-based optoelectronic devices.