Uniaxial Strain and Optical Properties of GaP Nanowires

Abstract

The optical properties for wurtzite (WZ) Bulk GaP and GaPnanowires (GaP-NWs) in hexagonal(circular), triangular and square cross sectional are investigated by using full potential linear augmented plane waves and local orbitals (FP-LAPW-LO) method based on density functional theory (DFT). The wurtzite nanowiresare investigated with diameters limited to ~27 oA. The optical functionsε_1 (ω),ε_2 (ω), n(ω), k(ω),σ(ω) and R(ω) as a function of photon energy have been investigated for unstrained bulk WZ-GaP and WZ-GaP-NWs in the first part. Finally, the optical functions are investigated for WZ-GaP-NWs by applying uniaxial strain from -5% to +5%. The effect of cross-sectional variation in the area and shape of the NWs on the optical functions is clear when compared with bulk GaP. GaP-NWs kept real dielectric constant ε_1 (ω) positive and refractive index n(ω) close to vacuum value for a wider range of energy on the contrary of bulk GaP. It is found that the dielectric constants ε_1 (ω) are slightly increased from the unstrained GaP-NWs values with strain increases. A shift in the threshold energy for ε_2 (ω) toward higher energy as the strain changes from tensile to compressive. The refractive index n(ω) shows a small change when passing from compressive toward tensile strain. It is found that GaP-NWs could play a role in solar cells structure and high-speed electronic circuits.