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Title: Optical studies of group III-nitride semiconductors
Author: Hammersley, Simon
ISNI:       0000 0004 2719 2807
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2012
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In this thesis I will discuss the results of optical spectroscopy measurements in relation to the study of quantum well and multiple quantum well structures made up of group III-nitride semiconductors. This will include the results of photoluminesence(PL), reflectance, and time resolved photoluminesence spectroscopy experiments as well as the results of time correlated single photon counting (TCSPC) experiments. I have investigated the droop in efficiency observed in InGaN/GaN quantum wells as the current density or excitation power density is increased. I will show that at the onset of the efficiency droop a simultaneous reduction in the S-shape temperature dependence of the peak emission energy shift is observed. These results suggest that one of the mechanisms behind the efficiency droop is the saturation of localised states as the density of carriers is increased. I also discuss the carrier dynamics in non-polar GaN/AlGaN quantum wells intersected by basal plane stacking faults (BSF)s. In order to describe the form of the results of TCSPC results I put forward a model for the transfer of carriers from the quantum well into the regions of the quantum well intersected by BSFs. Finally I show the results of an investigation into the features observed in photoluminesence excitation measurements by N Hylton et al [1, 2] near the GaN band gap. These features are caused by a red shift in the peak emission energy using the results of PL measurements made as a function of excitation photon energy it is possible to resolve the lowest energy feature observed by Hylton et al into two features. Two possible mechanisms are then discussed for how the excitation of carriers at set energies above the GaN band gap results in a change to the peak energy of the quantum well emission.
Supervisor: Dawson, Philip Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available