Influence of deep-pits on the device characteristics of metal-organic chemical vapor deposition grown AlGaN/GaN high-electron mobility transistors on silicon substrate

We have investigated the regions around deep-pits and their limitations on the performance of metal-organic chemical vapor deposition grown AlGaN/GaN high-electron-mobility transistors (HEMTs) on Si. The device characteristics such as maximum drain current density (IDSmax), threshold voltage (Vth), and three terminal-OFF breakdown (BVOFF) of a HEMT were affected based on the distance of deep-pits from a device active region. The deterioration of HEMT characteristics are significant if the active region is present within 50 μm radius of a deep-pit and becomes insignificant for distance beyond 50 μm. These device characteristics were compared with optical measurements and it was found the region around 50 μm radius of a pit have large dislocations and defects as confirmed by cathodoluminescence. Further, the E2 Raman shift measurements reveal additional stress in the 50 μm region around a pit.