Tuning the electronic and optical properties of two-dimensional GaN/AlGaN heterostructure by vacancy defect

In this paper, the effects of vacancy defects on electronic and optical properties of g-GaN/AlGaN and h-GaN/ AlGaN heterostructures are discussed based on first-principles. The stability, density of states, band structure, work function, absorption coefficient and reflectivity of heterostructures with different defects are analyzed in detail. Our results show that the g-GaN/AlGaN heterostructure is the most stable when the Al composition is 0.5 and the interlayer distance is 3 angstrom. When there are defects in heterostructures, the stability is reduced. The defected g-GaN/AlGaN heterostructure is more stable than h-GaN/AlGaN. The results of the band structure show that impurity levels can be observed because of the existence of surface dangling bonds between g-GaN layer and AlGaN layer, which is beneficial to electrons transition from conduction band to valence band. The band gap and work function results imply that N vacancy are more competitive for enhancing electronic performance of the heterostructure. The absorption coefficient and reflectivity show that N vacancy can also improve the optical properties of the heterostructure.