Small Signal Carrier Lifetime Measurements of InGaN / GaN Multiple Quantum Wells

Abstract

Understanding carrier dynamics in semiconductors is a complex task due to the entanglement of the various recombination processes. In order to further study these processes and their dependence on the instantaneous carrier concentration, this study aims to use the small signal differential lifetime method to isolate the Shockley-Read-Hall (SRH) process. This experiment including the electronic and optical setup, automation and data analyses was designed and justified. The setup and the calibration of measurements are detailed including modifications to the system. Two series of InGaN multiple quantum well samples were tested using this setup, one green and one blue emitting series. The samples within the series are grown using identical methods but with varying growth temperatures, thus altering their point defect density and subsequently the rate of SRH recombination. The power dependencies of the carrier lifetime associated with the SRH process are shown. Notably, two samples showed the presence of two different processes with different power dependencies, which could be due to different types of defect states in the samples. The other lifetimes measured, including the carrier lifetimes in the C5856 Blue 2 and C5858 Blue 3 samples, had some power dependency with increased power leading to a decrease in lifetime in some cases and an increase in others. This could be due to: an overlap with the B coefficient resulting in a component to the measured lifetime that decreases with power; saturation of localisation centres increasing the rate of SRH recombination; or saturation of defects, decreasing the rate of SRH recombination.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Binks (Supervisor) & Patrick Parkinson (Supervisor)