Intrinsic point defects in pristine and Zn-doped GaAs nanowire surfaces: A first-principles investigation

摘要

Utilizing first-principles calculations, we have systematically investigated on the impact of surface point defects on the stability, electronic and optical properties of pristine and Zn-doped Ga-As nanowires. Different defect types (antisite, interstitial and vacancy defect) and defect sites (surface, subsurface and core layer of nanowires) are considered to build defect models. Results show that As-Ga and Ga-As are respectively the most stable surface defect under As-rich condition and under Ga-rich condition, in both pristine and Zn-doped Ga-As nanowires. Compared with the pristine model, Zn-doped Ga-As nanowire will suffer a more significant surface defects under the same growth conditions due to lower formation energy. In addition, the band structure and electron density difference calculations indicate that Ga-As, As-in and V-Ga act as acceptors, while As-Ga, Ga-in and V-As act as donors. Interestingly, the incorporation of As-Ga defect will notably weaken the p-type character of Zn-doped Ga-As nanowires. Moreover, the optical absorption capability of pristine and Zn-doped Ga-As nanowires will be subject to varying degrees of variation after introducing different defects.