Optical studies of CdSe/ZnSe and CdSe/ZnBeSe Quantum Dots

• Main Authors: Wei-Hao Chen, 陳威豪
• Other Authors: Yang-Fang Chen
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/36501621554384009974

碩士 === 國立臺灣大學 === 物理學研究所 === 91 === In this thesis, we present a detailed study of optical properties of CdSe/ZnSe and CdSe/ZnBeSe quantum dots (QDs).grown by molecular beam epitaxy(MBE) on GaAs（001）substrates. The anomalous behavior of luminescence spectra is measured. Our results indicate that the formation of CdSe QDs as well as the II—VI/GaAs interface are modified by the presence of Be. I. Photoluminescence measurement (PL) Photoluminescence measurement has been carries out in two parts. Part Ι: PL measurement at 15 K We found that the strong blue-green emission peak and the narrower FWHM for CdSe QDs sandwiched by ZnBeSe compared to that of QDs sandwiched by ZnSe may be due to the smaller QD size and the higher uniformity in the ZnBeSe case. Part II: Temperature dependent of PL measurement Form the measurement of temperature dependent, we found that anomalous behaviors of photoluminescence (PL) spectra. This result implies that the effects of localization in the ZnBeSe sample do not play a significant role. II. Photoluminescence excitation (PLE) measurement By comparing the PL and PLE spectra, it was found that there is a large Stokes’ shift in the CdSe/ZnSe QDs case. The exciton localization effect is one of the main factors leading to the Stokes’ shift. III. Resonant photoluminescence (RPL) measurement In RPL spectra a redshift of the PL peak with increasing excitation photon-energy was observed. Comparing the results for the CdSe QDs grown on ZnSe and ZnBeSe, we see that the redshift of the PL peak energy of the ZnBeSe sample is greatly reduced.