結構不完美在自組性砷化銦奈米環的反磁性能量位移之影響：以理論計算方法

Abstract

在這份研究裡，我們使用映像法以及直接對角化法來計算激子在自組性半導體量子環的反磁性能量位移。映像法能夠在三維空間中描述該量子環的物質特性，而直接對角化法則提供了一個途徑來計算激子的能量以及波函數。我們從一個環緣上對稱地上下搖擺的量子環開始研究，該量子環有著鏡像對稱的位能。接著我們考慮結構上的不完美，我們假設這些不完美是由不對稱的環緣上搖擺以及由不平衡的位能造成的，鏡像對稱也因此消失。我們的模擬結果顯示，只要很小的結構上不完美會使激子的波函數掉到其中一個位能谷裡，且波函數的分布範圍大量的縮減。激子的反磁性能量位移也大量的變小因為反磁性能量位移正比於激子波函數的分布範圍。我們計算得到的激子激態能量以及反磁性能量位移都與實驗上測量到的數據吻合。

In this study we calculate the excitonic energy diamagnetic shifts in self-assembled semiconductor nano-rings using the mapping and exact diagonalization methods. The mapping method allows a three dimensional description of the ring and the exact diagonalization method gives a way to compute the excitonic energies and wave functions. We start from symmetrically wobbled quantum rings with the electronic confinement potentials possessing a reflectional symmetry on the $(110)$ plane. The structural imperfections are considered by applying small variations on the geometry and potential profile and thus the reflectional symmetry is broken. Our results show that with small structural imperfections the excitonic wave functions will be located in one of the potential valleys and the extension of the wave functions will shrink greatly. A dramatical decrease in the excitonic energy diamagnetic shift is observed because the diamagnetic shift depends on the effective area spanned by the excitonic wave function. The calculated excitonic ground state energies and diamagnetic shift coefficients are in good agreement with the experimental measurements.