Magneto-optical determination of the carrier lifetime in coherent Ge(1-x)Sn(x)/Ge heterostructures

TL;DR

This study uses magneto-optical techniques to measure carrier lifetimes in Ge(1-x)Sn(x) heterostructures, revealing sub-nanosecond effective lifetimes dominated by non-radiative recombination, which advances understanding of carrier dynamics in this material.

Contribution

It introduces a magneto-optical method to directly measure carrier dynamics in Ge(1-x)Sn(x) films, providing new insights into their recombination processes.

Findings

Carrier lifetime is in the sub-ns range at cryogenic temperatures.

Carrier recombination is dominated by non-radiative processes.

The method provides direct access to optically-induced carrier dynamics.

Abstract

We present a magneto-optical study of the carrier dynamics in compressively strained Ge(1-x)Sn(x) films having Sn compositions up to 10% epitaxially grown on blanket Ge on Si (001) virtual substrates. We leverage the Hanle effect under steady-state excitation to study the spin-dependent optical transitions in presence of an external magnetic field. This allowed us to obtain direct access to the dynamics of the optically-induced carrier population. Our approach singled out that at cryogenic temperatures the effective lifetime of the photogenerated carriers in coherent Ge(1-x)Sn(x) occurs in the sub-ns time scale. Supported by a model estimate of the radiative lifetime, our measurements indicate that carrier recombination is dominated by non-radiative processes. Our results thus provide central information to advance the fundamental understanding of carrier kinetics in this novel direct-gap group-IV material system. Such knowledge can be a stepping stone in the quest for the implementation of Ge(1-x)Sn(x)-based functional devices.