Low resistance Ti/Al/Au ohmic backside contacts to nonpolar m-plane n-GaN

An effective surface treatment method has been developed to realise low resistance ohmic contacts on the lapped backsides of m-plane n-GaN substrates with a moderate doping level of 5.5??10¹⁷ cm^-3. Ti/Al/Au contacts with fine polishing and an ICP treatment followed by annealing at 700??C for 5 min yielded a specific contact resistance as low as 3.9??10^-5 ??cm². The same low specific contact resistance was also achieved by annealing at 500??C for 5 min on a relatively rough surface. The effective removal of the lapping damage by ICP treatment and the creation of nitrogen vacancies during annealing are believed to improve the contacts.