磁場作用下之單一量子點分子能態

Abstract

本計畫目的是研究由雙層堆疊之砷化銦鎵量子點所形成的單一量子點分子在 磁場作用下之耦合能態，擬研究主題包含:（1）量子點分子之激子轉換機制以及（2） 量子點分子在磁場作用下之耦合效應。本計畫將運用超快時間解析光譜量測技術， 研究激子能量轉換的動態行為，並以顯微螢光激發能譜探索選擇性激發QDM 激子 態的可能性。此外，我們也將設計極化解析之光子相干量測研究QDM 中雙激子- 激子之序列輻射中所隱含的按激子態。顯微磁光光譜技術，藉由外加垂直（Faraday） 及水平（Vogit）方向的磁場，可以用來偵測量子點的反磁能移及奇曼（Zeeman） 效應。我們將利用這樣的技術，研究量子點大小、形狀及應力分佈對於g 值的影響， 並探討QDM 在磁場作用下的能態耦合現象。探討議題包括g 值的操控、輕-重電洞 能帶混和及明-暗激子混和。

This project is proposed to study the coupled energy states of single quantum-dot molecules (QDM) formed by single pairs of vertically coupled In(Ga)As quantum dots (QDs). The topics to be studied include: (1) The mechanism of exciton energy transfer in single QDMs and (2) The coupling effects of energy states in single QDMs under the influence externally applied magnetic field. Time-resolved micro-photoluminescence (μ-PL) will be employed to study the dynamics of exciton transfer in single QDMs at different temperatures. The feasibility of selective excitation of exciton states in single QDMs will be explored by μ-PL excitation spectroscopy. In addition, we will also set up an optical system to conduct polarization-resolved photon correlation measurements for the study of underlying dark exciton states involved in biexciton-exciton cascade emission processes in single QDMs. Magneto-μ-PL spectroscopy with external applied magnetic field up to B= 6 T in either Faraday or Vogit configurations can be utilized to measure the diamagnetic shift and Zeeman splitting in single QDs and QDMs. By these measurements, the impact of dot size, shape as well as non-uniformly strain field distribution on the g factor will also be discussed. The magnetic field induced coupling in energy states of single QDMs will also be investigated. The manipulation of g factor, valence band mixing between heavy-hole and light-hole states, as well as the mixing between bright and dark exciton states under the influence of external applied magnetic field will be discussed.