ENHANCED DOPING EFFICIENCY OF ULTRAWIDE BANDGAP SEMICONDUCTORS BY METAL-SEMICONDUCTOR ASSISTED EPITAXY

摘要

An epitaxial growth process, referred to as metal-semiconductor junction assisted epitaxy, of ultrawide bandgap aluminum gallium nitride (AIGaN) is disclosed. The epitaxy of AIGaN is performed in metal-rich (e.g., Ga-rich) conditions using plasma- assisted molecular beam epitaxy. The excess Ga layer leads to the formation of a metal-semiconductor junction during the epitaxy of magnesium (Mg)-doped AIGaN, which pins the Fermi level away from the valence band at the growth front. The Fermi level position is decoupled from Mg-dopant incorporation; that is, the surface band bending allows the formation of a nearly n-type growth front despite p-type dopant incorporation. With controlled tuning of the Fermi level by an in-situ metal- semiconductor junction during epitaxy, efficient p-type conduction can be achieved for large bandgap AIGaN.