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

• Main Authors: Son, Bongkwon, Zhang, Lin, Jung, Yongduck, Zhou, Hao, Nam, Donguk, Tan, Chuan Seng
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Electrical and electronic engineering::Semiconductors; GeSn Alloy; Silicon Photonics; Optoelectronic Integration
• Online Access: https://hdl.handle.net/10356/153005
• Institution: Nanyang Technological University

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 1,000 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.