Studies of Quantum Structures ofInAs and Related Material by hotoluminescence

• Main Authors: Chih-hao Wu, 吳志浩
• Other Authors: Shing-Long Tyan
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/12467897294628211688

博士 === 國立成功大學 === 物理學系碩博士班 === 93 === 　This dissertation consists of two parts :Studies of ultrathin InGaAs quantum wells grown at different temperatures by magneto-photoluminescence ;Investigation of quantum states in ultra small InAs/GaAs quantum dots by photoluminescence . 　The ultrathin single-quantum-well (QW) structures grown at different temperatures are studied using magneto-photoluminescence in magnetic fields of up to 15 T both parallel B|| and perpendicular B⊥ to the growth axis .The dimensionalities and effective diameters are deduced from the low field diamagnetic shift. The dimensionalities are approximately the same ,0.3 ,and the effective diameters obtained in B|| are almost the same for the QWs grown at different temperatures .The effective diameter measured in B⊥ is larger than that in B|| for the QW grown at high temperature while it becomes smaller than that in B|| for the QW grown at the lowest temperature due to the exciton localization .The anomalous diamagnetic shift shows a cusp approximately in 4T in B⊥,and the high-field diamagnetic shift can be well-described as B4/3-dependence based on the effective width well model . 　The quantum states of InAs/GaAs quantum dots (QDs) with a baselength of less than 10 nm are studied by the excitation- and temperature-dependent photoluminescence (PL) .The baselength of the QDs ,calculated by the PL ground state transition energy in agreement with the result of atomic force microscopy measurements .By means of the excitation-dependent PL ,we demonstrate that only the ground electron and hole states exist when the baselength of the QDs is smaller than about 7.3 nm ,whereas the larger dots with a baselength of about 8.7 nm will give rise to one excited hole state .The measured energy separation between the ground and the excited hole states is in good agreement with the theoretical calculation .The transition energy in temperature-dependent PL spectra shows a rapid redshift as the temperature is higher than the critical temperature .The redshift rate is about 2.8 and 2.5 times larger than the values calculated by Varshni's law for small and large dots respectively .The higher redshift rate can be explained by the stronger tunneling effect .In addition ,the PL linewidths show a V-shape dependence with the temperature .This behavior could be well described as a tunneling and electron- phonon scattering effect .