Structural Asymmetry Effects on the Optical Properties of InGaN Quantum Well

• Main Authors: Hsu Yi-chien, 徐易千
• Other Authors: Peng Lung-han
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/40202871587697118850

碩士 === 國立臺灣大學 === 光電工程學研究所 === 87 === In this thesis, the effects of structure asymmetry on the electronic and optical properties of indium gallium nitride ( InGaN ) quantum wells ( QWs ) are investigated. Using a self-consistent analysis, the dispersion relation of conduction- and valence- subbands can be calculated for InGaN QWs. It is found the spectrum red-shifting caused by piezoelectricity and many-body effects and blue-shifting caused by charge-screening and band-filling effects result in a gain competition process in InGaN QWs. Due to these interactions, a better carrier confinement and stronger charge screening of piezoelectric field can be found in the asymmetric GaN / InGaN /AlGaN QW. In addition, such mechanism provides a 10-fold increase in the TE-polarized optical gain compared with that in the symmetric InGaN / AlGaN QW case at high carrier injection regime (Ninj > 251019 cm-3). The asymmetric InGaN QW structure can also exhibit a spectral blue shift with respect to that of the symmetric QW case due to the diminishing of piezoelectricity-induced quantum confined Stark effect (PQCSE). The waveguide properties of published InGaN laser diode structure are also discussed by using finite difference method. There is a strong resonant coupling between the p-GaN guiding layer and the p-Al0.08Ga0.92N cladding layer. This is caused by the thin thickness of the 0.5mm cladding layer and the insufficient discontinuity in the index of refraction of p-Al0.08Ga0.92N cladding layer. The interaction of these two factors also introduces optical loss in this kind of laser diode structure.