Optimization of Fe doping at the regrowth interface of GaN for applications to III-nitride-based heterostructure field-effect transistors

Abstract

The authors have studied the effects of Fe doping at the interface between GaN epitaxial layers for heterostructure field-effect transistors grown by metal-organic chemical vapor deposition and the corresponding impact on the device characteristics. The epitaxial structures were grown with different Fe-doped GaN layers at the layer-template interface. Analysis of the measured electron and interface charge distributions in the heterostructures demonstrated the important role of Fe doping at the regrowth interface. No charge at the regrowth interface was observed in transistor structures with a thick Fe-doped layer. Characterization of the electrical properties of the transistor structures revealed the presence of high sheet carrier concentrations and improved mobilities with increasing thickness of the Fe-doped GaN layer at the regrowth interface.