Systematic study on photoexcited carrier dynamics related to defects in GeSn films with low Sn content at room temperature

Abstract

Germanium–tin (GeSn) alloys have received much attention thanks to their optical/electrical properties and their operation in the mid-infrared range. However, dislocations/defects in GeSn films serve as trap states, limiting radiative recombination/generation via band-edges. In this work, the impact of the trap states in GeSn with varying Sn contents is investigated. The systematic study reveals that the defects/dislocations in GeSn contribute to the carrier dynamics, mainly originated from the trap states near GeSn/Ge interface. Through photoluminescence (PL) study, the broad PL peak of the trap state for GeSn exists at ∼0.57 eV. The increase in Sn content mitigates the trap-related carrier dynamics. Besides, the increase in GeSn thickness effectively suppresses the interface-related carrier dynamic. By increasing thickness from 180 to ∼900 nm, the external quantum efficiency is enhanced by ∼10×. This study provides a comprehensive understanding of trap-related carrier dynamics in a GeSn material system at room temperature.

Metal-Semiconductor-Metal Photodetectors on a GeSn-on-Insulator Platform for 2 µm Applications

“…In order to reduce the leakge current for the GeSnOI photodetector, low Sn contents on insulator platforms is potentially attractive due to high-crystallinity of GeSn films [14,31]. In addition, the advanced surface passivation can reduce the surface leakage current for the photodetectors [32,33].…”

“…5. Benchmarking of the dark current density for the reported waveguide-shape GeSn photodetectors on the different platforms [10,23,[31][32]. Dark current density for each photodetector is benchmarked with respect to Sn content.…”