Quantum confinement in semiconductor random alloys: a case study on Si/SiGe/Si

TL;DR

This study investigates how nanoscale local composition fluctuations in SiGe/Si alloys affect electronic properties, comparing detailed calculations with a simplified quantum well model for potential device applications.

Contribution

It introduces an extended Hückel theory approach to analyze quantum confinement effects in SiGe/Si alloys, highlighting the importance of local fluctuations and validating a simplified quantum well model.

Findings

Local composition fluctuations significantly influence band alignment and band gap.

The quantum well model effectively captures the essential physics of the system.

Extended Hückel theory provides insights into nanoscale alloy behavior.

Abstract

Local composition fluctuations in random alloys become crucial when one or more dimensions are reduced to the nanoscale. Using extended H\"uckel theory, we study the semiconductor random alloy SiGe sandwiched between Si due to its relevance for transistor devices. We evaluate the effects of the alloy composition, layer thickness, and local fluctuations of the Ge concentration on the band alignment and the band gap. The results are compared with the finite quantum well model. That model captures the essential physics and can act as a computationally faster alternative.