Confirmation of the compensation of unintentional donors in AlGaN/GaN HEMT structures by Mg-doping during initial growth of GaN buffer layer

Abstract

Effect of partial Mg doping on the compensation of unintentional donors at epilayer/template interface and in the GaN channel layer of AlGaN/GaN High Electron Mobility Transistor (HEMT) structures is investigated. Photoluminescence excitation spectroscopy and surface photovoltage spectroscopy measurements reveal the signature of high density of unintentional shallow donors and deep level defects throughout the GaN buffer layer along with a strong dominance at the GaN/Fe-GaN template interface. Mg doping during the initial growth of GaN buffer layer on Fe-GaN template is found to compensate unintentional donors which therefore reduces the density of deep defects. Hall measurements also confirm systematic improvement in the electronic transport properties of AlGaN/GaN HEMT for an optimized Mg doping. Further, Mg-doping driven enhancement of 2-dimensional electron gas confinement at AlGaN/GaN interface is also observed in the spectroscopy measurements. It is shown that the electrical and optical properties can be improved by an optimized Mg-doping of the initial part of GaN buffer layer in AlGaN/GaN HEMT structures.