Interactions between a Point-Defect State and Electron Quantum States in Inas Self-Assembled Quantum Dots
|關鍵字:||砷化銦量子點;電子放射;點缺陷;量子能階;導納頻譜分析;InAs quantum dots;electron emission;point defects;quantum states;admittance spectroscopy|
子能帶結構方面。第一年，我們將使用分子束磊晶(molecular beam epitaxy, MBE)成長樣
品， 將一些缺陷能階佈值在量子點內部或是其周圍， 首先利用光激螢光技術
(photoluminescence, PL) 與穿透式電子顯微鏡(cross-sectional transmission electron
spectroscopy)、深層能階展態頻譜(deep-level transient spectroscopy, DLTS)以及電容-時間
暫態頻譜(capacitance-time C(t) transience)等分析技術，期望能獲得缺陷與量子點能階，
InAs/GaAs self-assembled quantum dots (QDs) have recently attracted considerable attention for both theoretical and experimental studies due to promising technological applications. Many works have focused on experimentally determining the electronic band structure of the QD by analyzing electron emission from the QD. However, this emission time is very short and difficult to resolve due to the presence of significant tunneling. On the other hand, deep traps with their strongly localized wave functions have been proposed as local probes for characterizing electronic band structure. The change of the surrounding environment around the defect traps is expected to affect the emission parameters of the defect traps. However, in order to achieve this purpose, there are some requirements for the traps. For one thing, the trap has a high regularity: its capacitance-time transience for electron emission is exponential so that its emission energy can be accurately obtained. In the past years, we have studied many defect traps and found some suitable traps. One example is a trap associated with misfits induced by strain relaxation. This trap is well confined in certain region and its electron-emission properties are strongly affected by their surrounding environment. Thus, in this three year proposal, we intend to explore the possibility of using these traps as local probes for the electronic band structure of the QD. In the first year, we will use molecular beam epitaxy (MBE) to incorporate some defect states inside and near the QDs. The effect of these defects on the QDs will first be investigated by photoluminescence (PL) and cross-sectional transmission electron microscopy (TEM). In the electrical characterizations, we intend to combine admittance spectroscopy, deep-level transient spectroscopy (DLTS) and capacitance-time C(t) transience to obtain a wide temperature spectrum of the emission parameters of the defect states and the QD states. Beside the MBE growth, we will also induce defects in the QDs by implantation of such as N followed by thermal annealing. During the second year, the properties of electron emission from these defect states and from the QD confinement state will be thoroughly characterized. The interaction between the defect state and QD quantum state will be established. This study may provide another method for the modification of the electrical properties of the QDs. During the third year, we will focus on the effect of post-growth annealing on the defect states. This study is pioneering and is expected to be fruitful both in scientific studies and future applications.