Localized Energy States Induced by Atomic-Level Interfacial Broadening in Heterostructures

TL;DR

This paper develops a theoretical model to describe how atomic-level interfacial broadening in heterostructures creates localized energy states, affecting electronic and optical properties, and confirms these effects experimentally.

Contribution

It introduces a new theoretical framework that incorporates atomic-scale interfacial details to predict localized energy levels in heterostructures, validated by experimental data.

Findings

Localized energy levels are predicted in ultrathin heterostructures due to interfacial broadening.

Experimental confirmation of interfacial electronic transitions between 2 and 2.5 eV.

The model enables non-destructive probing of atomic-level interfacial broadening.

Abstract

A theoretical framework incorporating atomic-level interfacial details is derived to include the electronic structure of buried interfaces and describe the behavior of charge carriers in heterostructures in the presence of finite interfacial broadening. Applying this model to ultrathin heteroepitaxial (SiGe)m/(Si)m superlattices predicts the existence of localized energy levels in the band structure induced by sub-nanometer broadening, which provides additional paths for hole-electron recombination. These predicted interfacial electronic transitions and the associated absorptive effects are confirmed experimentally at variable superlattice thickness and periodicity. By mapping the energy of the critical points, the optical transitions are identified between 2 and 2.5 eV thus extending the optical absorption to lower energies. This phenomenon enables a straightforward and non-destructive probe of the atomic-level broadening in heterostructures.