Electronic and optical properties of beryllium chalcogenides/silicon heterostructures

TL;DR

This study models the electronic and optical properties of Si/BeSe0.41Te0.59 heterostructures and superlattices, revealing type II band alignment and interface states that influence optical transitions.

Contribution

It introduces a semiempirical tight-binding approach considering band bowing and offset measurements to analyze Si-based heterostructures with novel interface states.

Findings

Type II heterostructure with conduction band in Si and valence band in BeSe0.41Te0.59

Presence of interface states within Si bandgap

Optical edges below bulk Si bandgap and optically allowed transitions

Abstract

We have calculated electronic and optical properties of Si/BeSe$_{0.41}$Te$_{0.59}$ heterostructures by a semiempirical $sp^{3}s^{*}$ tight-binding method. Tight-binding parameters and band bowing of BeSe$_{0.41}$Te$_{0.59}$ are considered through a recent model for highly mismatched semiconductor alloys. The band bowing and the measurements of conduction band offset lead to a type II heterostucture for Si/BeSe$_{0.41}$Te$_{0.59}$ with conduction band minimum in the Si layer and valence band maximum in the BeSe$_{0.41}$Te$_{0.59}$ layer. The electronic structure and optical properties of various (Si$_{2})_{n }$/(BeSe$_{0.41}$Te$_{0.59})_{m}$ [001] superlattices have been considered. Two bands of interface states were found within the bandgap of bulk Si. Our calculations indicate that the optical edges are below the fundamental bandgap of bulk Si and the transitions are optically allowed.