Study of Extending Carrier Lifetime in ZnTe QD Coupled with ZnCdSe QW Grown by Molecular Beam Epitaxy

• Main Authors: Li, Jain-De, 李建德
• Other Authors: Chou, Wu-Ching
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/43308019831596730136

碩士 === 國立交通大學 === 電子物理系所 === 102 === In this work, we demonstrated the growth of a self-assembled type-II ZnTe/ZnSe quantum dot (QD) structure coupled with a type-I Zn0.88Cd0.12Se/ZnSe quantum well (QW) on the (001) GaAs substrate by molecular beam epitaxy (MBE). As the spacer thickness is less than 2nm, the carrier lifetime increasing from 20ns to 130ns was successfully achieved. By utilizing the time-resolved photoluminescence (TRPL) and PL with difference excitation wavelength and power, we identify the PL emission from the coupled QDs consists of two recombination mechanism. One is the recombination between electrons in ZnSe barrier and holes confined within ZnTe QDs, and the other is between electrons confined in Zn0.88Cd0.12Se QW and holes confined within ZnTe QDs. According to the band diagram and power-dependent PL, both of the two recombinations reveal the type-II transition. Based on the fitting of time-resolved PL decay curve, the lifetime of the first recombination remains about 10 ns, while that of the second recombination increases with decreasing spacer thickness. In addition, the second recombination mechanism dominates the whole carrier recombination as the spacer thickness is less than 2nm. A significant extension of carrier lifetime by increasing the electron – hole separation is illustrated in a type-II ZnTe/ZnSe QD structure coupling with a type-I ZnCdSe/ZnSe QW.