GeSn Defects and their Impact on Optoelectronic Properties: A Review

TL;DR

This review discusses the role of defects in GeSn semiconductors, highlighting their impact on optoelectronic properties and outlining challenges and future directions for improving material quality for device applications.

Contribution

It provides a comprehensive overview of GeSn defect types, their effects on electronic properties, and synthesizes fabrication and characterization techniques to guide future research.

Findings

Defects significantly affect carrier mobility and lifetime in GeSn.

Current fabrication methods have limitations in defect control.

Understanding defect mechanisms is crucial for device optimization.

Abstract

GeSn has emerged as a promising semiconductor with optoelectronic functionality in the mid-infrared, with the potential of replacing expensive III-V technology for monolithic on-chip Si photonics. Multiple challenges to achieve optoelectronic-grade GeSn have been successfully solved in the last decade. We stand today on the brink of a potential revolution in which GeSn could be used in many optoelectronic applications such as Light Detection and Ranging (LiDARs) devices and lasers. However, the limited understanding and control of material defects represents today a bottleneck in the performance of GeSn-based devices, hindering their commercialisation. Point and linear defects in GeSn have a strong impact on its electronic properties, namely unintentional doping concentration, carrier lifetime and mobility, which ultimately determine the performance of optoelectronic devices. In this review, after introducing the state-of-the-art of the fabrication and properties of GeSn, we provide a comprehensive overview of the current understanding of GeSn defects and their influence on the material (opto)electronic properties. Throughout the manuscript, we highlight the critical points that are still to solve. By bringing together the different fabrication techniques available and characterizations realized we provide a wholistic view on the field of GeSn and provide elements on how it could move forward.