Mapping of Electronic Band Gap along the Axis of Single InAs/InSbxAs1-x Heterostructured Nanowire

TL;DR

This study maps the electronic band gap variation along single InAs/InSbAs nanowires using resonance Raman imaging and density functional theory, revealing a graded fundamental gap due to alloy composition tuning.

Contribution

It introduces a combined experimental and theoretical approach to map and understand the graded electronic band gap in heterostructured nanowires.

Findings

Observed axial variation of the band gap energy in nanowires.

Correlated experimental Raman data with theoretical band structure calculations.

Proposed a model for graded fundamental gap energy along the nanowire axis.

Abstract

We report the graded electronic band gap along the axis of individual heterostructured WZ-ZB InAs/InSb0.12As0.88 nanowires. Resonance Raman imaging has been exploited to map the axial variation in the second excitation gap energy (E1) at the high symmetry point (L point) of the Brillouin zone. We relate the origin of the observed evolution of the gap energy to the fine tuning of the alloy composition from the tip towards the interface of the nanowire. The electronic band structures of InAs, InSb and InSbxAs1-x alloy systems at x=0.125, 0.25, 0.50, 0.75 and 0.875, using all electron density functional theory code Wien2k, are reported. The measured band gap along the axis of the InAs/InSb0.12As0.88 nanowire is correlated with the calculated gap energy at the A point and the L point of the Brillouin zone for InAs and InSb0.125As0.875, respectively. We draw a one-to-one correspondence between the variation of the E1 gap and the fundamental E0 gap in the calculated electronic band structure and propose the graded fundamental gap energy across the axis of the nanowire.