Investigation of Polarization-Related Effect on Blue InGaN Light-Emitting Diodes

碩士 === 國立彰化師範大學 === 光電科技研究所 === 96 === The polarization effect is an essential characteristic for the III-nitride materials. The existence of the strong electrostatic fields、which are generated by the spontaneous and piezoelectric polarizations、has a significant influence on the band profile、especia...

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Bibliographic Details
Main Authors: Miao-Chan Tsai, 蔡妙嬋
Other Authors: Yen-Kuang Kuo
Format: Others
Language:zh-TW
Published: 2008
Online Access:http://ndltd.ncl.edu.tw/handle/61436235027366543125
Description
Summary:碩士 === 國立彰化師範大學 === 光電科技研究所 === 96 === The polarization effect is an essential characteristic for the III-nitride materials. The existence of the strong electrostatic fields、which are generated by the spontaneous and piezoelectric polarizations、has a significant influence on the band profile、especially in quantum well region、and also results in quantum confined Stark effect and poor electron-hole overlap. Consequently、the radiative recombination rate、internal quantum efficiency、and optical performance of the light-emitting diodes are limited. Several research groups have focused on how the electrostatic fields might be removed and how the band bending situation might be improved. In this thesis、the effect of polarization on the blue InGaN light-emitting diodes has been numerically investigated. In addition、the appropriate design of the structure is proposed to enhance the optical characteristics of the light-emitting diodes. In chapter 1、the literatures and papers related to the concept of polarization-related effect are introduced and the calculation method of polarization charges is also described. In chapter 2、the structure of the blue light-emitting diode under study and the physical parameters used in APSYS simulation program are introduced. In chapter 3、the effect of spontaneous and piezoelectric polarizations on optical characteristics of the blue InGaN light-emitting diode is investigated. The band diagrams、overlap between electron and hole wavefunctions、electrostatic fields、distribution of electron and hole carriers、and radiative recombination rate are analyzed and compared. In chapter 4、for the blue InGaN light-emitting diodes、the quaternary AlGaInN polarization-matched electron-blocking layer and barrier layers are utilized to reduce the polarization effect. Furthermore、the optimization of the optical performance is attempted by using proper AlGaInN epitaxial layer. In chapter 5、the effect of the staggered quantum well upon the blue InGaN light-emitting diodes is numerically studied. Moreover、the optimized staggered quantum well structure is demonstrated、and the physical origins for the improvement in optical performance are figured out. Finally、a summary to the previous studies is provided in chapter 6.