Substitutional and vacancy defects in two-dimensional AlSb: A first principle approach

Abstract

AlSb is a semiconductor material which exist in 3D as well as 2D regimes. AlSb have a high electron mobility which is useful for application in high speed electronic devices. AlSb has potential applications in radiation detection. Defects, including intrinsic and extrinsic have been shown to influence the performance of AlSb for applications in electronic and optoelectronics. In this thesis, density functional theory with the aid of the generalised gradient approximation was use to model the stability as well as the formation of Al and Sb vacancies, Li and Be substitutions in 2D hexagonal AlSb. The structural and electronic properties of the aforementioned defects in AlSb were reported. Under equilibrium conditions, the aluminium vacancy (V Al ) is energetically more favourable than the antimony vacancy (V Sb ). While the Be substitution is more stable at the Al atomic site, the Li substitution is more stable at the Sb atomic site. The defects investigated modulated the band gap of the AlSb. Whereas the p orbital of the Sb atom contributed the dominant states in the band gap of the host for all the defects, the p orbital of Al contributed immensely to the defects states. The results further shows that using the generalised gradient approximation predicts defective AlSb as well as the pristine AlSb to be metallic. This has paved the way for further investigation using more accurate exchange correlation approximations.