Dependence of Ti/C ratio on Ohmic contact with tic electrode for AlGaN/GaN structure

The dependency of Ti atom composition in Ti-C mixed electrodes on Ohmic characteristics for AlGaN/GaN structure is examined by elucidating the role of both Ti and C atoms. Owing to AlGaN surface reduction by reaction with C atoms with thermal treatment, an enhanced reaction of Ti atoms and AlGaN layer has been confirmed. The border of reactive layer and the remaining AlGaN layer has shown rather uniform interface, which is contrast to conventional metallic spike formation. Higher Ti atom composition has revealed lower Ohmic contact resistance, especially 2.6 Ωmm with Ti:C of 5:1. The proposed reaction mechanism gives a new guideline to achieve uniform electron conduction for lower contact resistance.