Beryllium doped semi-insulating GaN without surface accumulation for homoepitaxial high power devices

Abstract

Semi-insulating GaN films with controlled dopant profiles have significant potential to improve the performance of high-power electronics. Beryllium doped GaN (GaN:Be) films previously demonstrated a semi-insulating nature, but the Be-dopant profiles in these films exhibited Be surface segregation and accumulation, which would lead to undesired leakage current paths in devices and deterioration of breakdown voltage. Improved growth kinetics of metal modulated epitaxy at low growth temperatures are applied in the study of GaN:Be films to achieve selectively controlled and abrupt step-doped Be profiles. The GaN:Be films were found to be semi-insulating via Hall effect measurements at elevated temperatures of 495 K. The films were shown to effectively electrically compensate surface contaminants at regrowth interfaces. Surface contaminants (O, Si, and C) typically result in unintentional n-type doping at the GaN on GaN regrowth interface. In order to demonstrate the utility of Be doping, GaN:Mg p-type films are grown atop GaN:Be buffer, AlN buffer, and control samples without any insulating buffer on GaN:Fe templates. Remarkably, the p-type films grown atop control samples up to 400 nm thick are compensated from surface contaminants, whereas the films grown atop AlN and GaN:Be insulating layers effectively electrically neutralize the surface contaminants and result in high hole concentrations of 2.3 and 2.5 × 1019 cm−3, respectively. The use of GaN:Be instead of AlN buffers eliminates the need to deconvolve the effects of the AlN/GaN 2D sheet charges and defects from lattice mismatch, removes lateral conduction paths, and reduces inherently high static vertical electric fields that detract from power device performance.