Significant increase in conduction band discontinuity due to solid phase epitaxy of Al_2O_3 gate insulator films on GaN semiconductor

摘要

We have investigated band discontinuities and chemical structures of Al_2O_3 gate insulator films on n-type GaN semiconductor by photoemission and x-ray absorption spectroscopy. It is found that the solid phase epitaxy at the GaN crystal during annealing procedures at 800 ℃ leads to phase transformation of Al_2O_3 films from amorphous to crystalline. Changes in crystallographic structures closely correlate with the significant increase in conduction band discontinuity at the Al_2O_3/GaN interface, which suggests that epitaxial Al_2O_3 films on GaN semiconductor, free from grain boundaries of Al_2O_3 polycrystalline, hold the potential for high insulation performance.