第二型能帶結構硒化錳鋅/碲硒化鋅多重量子井之光學特性研究

Abstract

利用光激螢光量測技術來分析硒化錳鋅/碲硒化鋅(碲含量佔8和20莫耳百分比)多重量子井之光學特性。此多重量子井是以分子束磊晶系統所成長，碲硒化鋅層井寬分別為2、3和5奈米。隨著雷射功率強度的增加，量測到光激螢光光譜峰值有明顯的藍位移，這是能帶彎曲效應所造成，由此可以驗證此多重量子井是第二型能帶結構。由光激螢光變溫光譜實驗，可求得樣品的活化能。我們也利用時間解析光譜實驗分析載子的複合機制，發現載子的生命期會隨著不同的碲含量以及碲硒化鋅厚度而改變，這是因為電子與電洞的波函數重疊情形受到了改變。時間解析光譜隨雷射功率強度而呈現的非單一指數曲線，也可以用能帶彎曲模型解釋。

The Zn0.97Mn0.03Se/ZnSe1-xTex (x = 0.08 and 0.20) multiple quantum wells (MQWs) grown by molecular beam epitaxy were studied by photoluminescence (PL) measurements. The ZnSe1-xTex well thickness varies among 2, 3, and, 5 nm. The PL peak energy shows a giant blue-shift with excitation power due to the band-bending effect. The activation energies of the MQWs were also obtained by temperature-dependent PL measurements. We also studied the mechanism of carrier recombination by the time-resolved photoluminescence (TRPL) experiments. The dependence of PL lifetimes on the Te concentration and well width can be explained by the variation of electron-hole wavefunction overlapping. Moreover, the non-single-exponential PL decays of the power-dependent TRPL measurements can be understood by the band-bending model.