Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors

In this thesis, the electronics band structures of wurtzite ZnO bulk materials is studied theoretically based on Empirical Pseudopotential Method (EPM) and 6-band k•p Hamiltonian. Furthermore, confined exciton state in Quantum Wells (QWs) is studied theoretically. By using the k•p Hamiltonian and va...

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Main Author: Abiyasa, Agus Putu
Other Authors: Yu Siu Fung
Format: Theses and Dissertations
Language:English
Published: 2008
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Online Access:https://hdl.handle.net/10356/13288
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-132882023-07-04T17:23:56Z Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors Abiyasa, Agus Putu Yu Siu Fung School of Electrical and Electronic Engineering DRNTU::Engineering::Electrical and electronic engineering::Semiconductors In this thesis, the electronics band structures of wurtzite ZnO bulk materials is studied theoretically based on Empirical Pseudopotential Method (EPM) and 6-band k•p Hamiltonian. Furthermore, confined exciton state in Quantum Wells (QWs) is studied theoretically. By using the k•p Hamiltonian and variational calculation with biaxial strain and exciton-phonon interactions taken into consideration, excitonic optical gain of MgxZn1-xO/ZnO QWs is deduced. From the available experimental data, the band offset and conduction band deformation constant of MgxZn1-xO/ZnO QWs are calculated to be 60/40 and -6.8 eV, respectively. On the other hand, the recombination process due to free exciton state that contributed to random lasing action in highly disordered ZnO polycrystalline films is investigated experimentally. The intrinsic ZnO recombination processes that contribute to random lasing are found to be free-exciton, exciton-exciton scattering or electron hole plasma (EHP) depending on the conditions of ZnO films. The influence of mechanical strain, temperature, and pumping profile on the random lasing mechanisms inside highly disordered ZnO polycrystalline films are then investigated. It is found that 1) the stimulated emission inside ZnO films can be related to free-exciton or EHP depending on the variation of Mott’s density which can be controlled by the mechanical strain, 2) the sustainability of high temperature random lasing action inside ZnO films is due to the strong confinement of excitons inside the ZnO grains and 3) the formation of closed-loop random lasing inside the ZnO films is dependent on optical gain profile which is determined by the operating temperature and pump beam profile. DOCTOR OF PHILOSOPHY (EEE) 2008-09-10T09:02:21Z 2008-10-20T07:23:12Z 2008-09-10T09:02:21Z 2008-10-20T07:23:12Z 2008 2008 Thesis Abiyasa, A. P. (2008). Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/13288 10.32657/10356/13288 en 150 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Electrical and electronic engineering::Semiconductors
spellingShingle DRNTU::Engineering::Electrical and electronic engineering::Semiconductors
Abiyasa, Agus Putu
Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors
description In this thesis, the electronics band structures of wurtzite ZnO bulk materials is studied theoretically based on Empirical Pseudopotential Method (EPM) and 6-band k•p Hamiltonian. Furthermore, confined exciton state in Quantum Wells (QWs) is studied theoretically. By using the k•p Hamiltonian and variational calculation with biaxial strain and exciton-phonon interactions taken into consideration, excitonic optical gain of MgxZn1-xO/ZnO QWs is deduced. From the available experimental data, the band offset and conduction band deformation constant of MgxZn1-xO/ZnO QWs are calculated to be 60/40 and -6.8 eV, respectively. On the other hand, the recombination process due to free exciton state that contributed to random lasing action in highly disordered ZnO polycrystalline films is investigated experimentally. The intrinsic ZnO recombination processes that contribute to random lasing are found to be free-exciton, exciton-exciton scattering or electron hole plasma (EHP) depending on the conditions of ZnO films. The influence of mechanical strain, temperature, and pumping profile on the random lasing mechanisms inside highly disordered ZnO polycrystalline films are then investigated. It is found that 1) the stimulated emission inside ZnO films can be related to free-exciton or EHP depending on the variation of Mott’s density which can be controlled by the mechanical strain, 2) the sustainability of high temperature random lasing action inside ZnO films is due to the strong confinement of excitons inside the ZnO grains and 3) the formation of closed-loop random lasing inside the ZnO films is dependent on optical gain profile which is determined by the operating temperature and pump beam profile.
author2 Yu Siu Fung
author_facet Yu Siu Fung
Abiyasa, Agus Putu
format Theses and Dissertations
author Abiyasa, Agus Putu
author_sort Abiyasa, Agus Putu
title Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors
title_short Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors
title_full Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors
title_fullStr Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors
title_full_unstemmed Investigation of excitonic recombination and its influence on random lasing phenomenon in ZnO semiconductors
title_sort investigation of excitonic recombination and its influence on random lasing phenomenon in zno semiconductors
publishDate 2008
url https://hdl.handle.net/10356/13288
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