MOCVD Regrown Ohmic Contacts to AlGaN/GaN Heterostructures

​AlGaN/GaN transfer length method (TLM) and Hall devices were fabricated with n+ doped GaN recessed Ohmic contact regions by metal-organic chemical vapor deposition (MOCVD) regrowth technology. The impact of MOCVD regrowth temperature and precursor flow rates on the quality and growth rate of n+ GaN were qualitatively evaluated through scanning electron microscopy (SEM). Ti/Al/Pt/Au metallized regrown n+ GaN Ohmic contacts exhibited a minimum specific contact resistivity of ​1.3 x 10​-3 ​Ωcm​2 and sheet resistance of 150 Ω/sq. It is hypothesized that carbon traces remaining on the AlGaN/GaN samples prior to re-entering the MOCVD chamber for regrowth is the cause of abnormal porous regions and defect density in the n+GaN film and the subsequently high specific contact resistivities.