砷化銦單量子點偏振螢光之光譜研究

Abstract

砷化銦單量子點的激子螢光具有精細結構分裂以及偏振不對稱性，且兩者彼此相關。激子螢光的精細結構分裂源於量子點的形狀不對稱，而偏振不對稱性則是由平面上應變不對稱造成的重電洞能態和輕電洞能態混合所引起。本文中將根據Bir-Pikus漢米爾頓方程式，探討精細結構分裂、重電洞能態和輕電洞能態混合以及偏振不對稱性之間的相互作用。此外，我們可以利用外加水平磁場改變激子能態的精細結構分裂，使其值由負值隨著磁場增加而變為正值。當精細結構分裂為零，激子能態即為簡併。

The fine structure splitting (FSS) and polarization anisotropy (PA) of exciton emissions from single InAs/GaAs quantum dots (QDs) are investigated. A systematic correlation between the FSS and PA is observed. The excitonic FSS is attributed to the QD shape asymmetry reduction, while the PA is a direct consequence of the mixing between the heavy-hole (hh) and light-hole (lh) states due to the anisotropy in-plane strain distribution. Based on the formulism of the Bir-Pikus Hamiltonian, the interplay between the FSS, the hh-lh mixing, as well as the PA are discussed. An in-plane magnetic field is used to manipulate the excitonic FSS in QDs. We find that, for QDs with negative FSS, the degeneracy of the exciton states can be recovered under an in-plane magnetic field.