Determination of the valence band offset at cubic CdSe/ZnTe type II heterojunctions: A combined experimental and theoretical approach

TL;DR

This paper combines experimental photoluminescence measurements and theoretical tight-binding calculations to accurately determine the valence band offset at cubic CdSe/ZnTe heterojunctions, providing a reliable method for such interface characterizations.

Contribution

It introduces a combined experimental-theoretical approach using PL and tight-binding models to determine valence band offsets in cubic heterojunctions.

Findings

PL-based method yields precise VBO measurements

Tight-binding calculations accurately reproduce band structures

Results show good agreement between experiment and theory

Abstract

We present a combined experimental and theoretical approach for the determination of the low-temperature valence band offset (VBO) at CdSe/ZnTe heterojunctions with underlying zincblende crystal structure. On the experimental side, the optical transition of the type II interface allows for a precise measurement of the type II band gap. We show how the excitation-power dependent shift of this photoluminescence (PL) signal can be used for any type II system for a precise determination of the VBO. On the theoretical side, we use a refined empirical tight-binding parametrization in order to accurately reproduce the band structure and density of states around the band gap region of cubic CdSe and ZnTe and then calculate the branch point energy (also known as charge neutrality level) for both materials. Because of the cubic crystal structure and the small lattice mismatch across the interface, the VBO for the material system under consideration can then be obtained from a charge neutrality condition, in good agreement with the PL measurements.