New Model of Fe Diffusion in Highly Resistive Fe-Doped Buffer Layer for GaN High-Electron-Mobility Transistor

We demonstrated the suppression of Fe incorporation into undoped GaN layers grown on an Fe-doped GaN layer by metal organic chemical vapor deposition (MOCVD). Our systematic study of the depth profile of Fe doping by secondary-ion mass spectrometry (SIMS) revealed that Fe segregation on the growth surface is responsible for Fe incorporation into the upper undoped GaN layer. Moreover, we confirmed from the Fe doping profiles of strain-varied undoped GaN layers grown on an Fe-doped AlxGa1-xN layer that the compressive strain on the growth surface could effectively suppress Fe segregation. In this study, we propose a new model showing that the suppression is due to an increase in the extent of thermal desorption of Fe from the growth surface by compressive strain.