Examination of doping limits in GaN:Mg layers for superjunction devices

Abstract

With the promise of lower specific on resistances and higher breakdown voltages, superjunction devices can be employed to improve power efficiency. GaN superjunction devices, however, have mostly been achieved through heterojunction structures. One reason for this is the traditionally accepted need for higher doping in GaN:Mg layers to maintain reasonable conduction. In this work, we examine the lower doping limits of GaN:Mg layers to facilitate charge balancing in superjunction structures. Circular transmission line measurements, temperature-dependent Hall effect, capacitance–voltage, and SIMS analysis show that layers grown from NH3-MBE of targeted [Mg] between 5 × 1017 and 1 × 1019 cm−3 are capable of being employed in superjunction device architectures. When the layer doping is reduced to 2 × 1017 cm−3, the layer is compensated and unable to function as a p-type layer for charge balancing. This provides a reasonable parameter space for GaN:Mg layers in future GaN superjunction devices.