Structural and electronic properties of AlGaN nanowires modulated by Al component and sectional size: A first principles study with DFT+U method

Abstract

AlGaN nanowires have plenty of applications in optoelectronic functional devices. However, the electronic characteristics and stability of AlGaN nanowires are rarely explored, especially for an actual prediction of bandgaps with varying Al components. In this work, we utilize first principles calculation with DFT + U method to study the stability, charge redistribution, band structures, density of states of Al_xGa_1-xN alloy nanowires with x spanning from 0 to 1. The results indicate that the stability of the nanowire is enhanced with increasing nanowire diameter and Al component. The bond length in the outermost layer, vertical to the specified direction, is stretched as the Al component increases. The bandgap of nanowire is larger than that of bulk phase and the bowing parameter of nanowire is relatively low. According to the analysis of density of states (DOS), the migration of band structures is attributed to N-p states at VBM and Ga-s and Al-p states at CBM. The calculation of Crystal Orbital Hamilton Population (COHP) reveals the variation of bandgap with changing Al component and diameter. According to the analysis of electron density difference and charge transfer, Al atom has a stronger electron negativity and the electron density surrounding Ga is more delocalized compared Al atom. The results obtained in this study is expected to give some guidance for the preparation of optoelectronic devices based on AlGaN nanowires.