砷化銦/砷化銦鎵量子點中砷化銦厚度對缺陷的電子放射與捕捉影響之研究

Abstract

本論文主要探討以分子束磊晶所成長的InAs/InGaAs Dots-in-Well結構之電、光特徵。我們製作不同InAs厚度的樣品，厚度有1.97 ML、2.34 ML、2.7 ML、3.06 ML以及3.33 ML。隨著InAs厚度增加，波長往長波長移動，其中1.97 ML，2.34 ML以及2.7 ML樣品室溫發光波長各為1238nm，1300nm與1310nm。當InAs 厚度繼續增加至3.06 ML時，樣品的波長產生藍移至1223nm，而厚3.33 ML的樣品發光波長亦產生藍移至1215nm，表示成長InAs材料有一臨界厚度介於2.7∼3.06 ML。另外從C-V量測顯示出2.34 ML樣品在DWELL結構中具有載子推積現象，表現出量子點的特性。但是對於3.06 ML及3.33 ML兩片樣品，C-V的峰值強度比2.34 ML樣品要弱很多，而且在這兩片樣品裡發現載子空乏的現象，空乏現象是發生在InAs靠近基板的那一邊，這顯示3.06 ML與3.33 ML兩片樣品量子點厚度已經超過臨界厚度，發生晶格鬆弛進而產生缺陷。此電性C-V量測與光性PL的觀測結果一致。另外經由深層能階暫態頻譜的量測我們得到，InAs厚度為3.06 ML及3.33 ML兩片樣品的缺陷活化能分別是0.37eV與0.41eV。透過DLTS我們也發現這兩片樣品具有捕捉位能障，經由改變填充偏壓時間的實驗，我們找出3.06 ML與3.33 ML兩片樣品各具0.1eV與0.22eV的捕捉位能障大小。

In this study, we have investigated the InAs/InGaAs (dots-in-a -well) structure with different InAs thickness . Red shift of Photoluminescence (PL) spectroscopy is observed from 1238nm to 1310nm as the InAs thickness increases from 1.97 to 2.7 ML. A significant reduction of the PL intensity is accompanied with a blue shift for 3.06 ML and 3.33 ML samples, indicating that there is a critical thickness in the InAs growth. The capacitance-voltage (C-V) measurement shows a carrier confinement for 2.34 ML sample. With increasing the InAs thickness to 3.06 and 3.33 ML, a significant carrier depletion caused by relaxation is observed near the bottom InAs/GaAs interface. Traps at 0.37eV and 0.41eV are measured by DLTS in 3.06 ML and 3.33 ML samples, respectively. These two traps are suggested to cause the carrier depletion. DLTS measurements have also provided an evidence of the capture barriers Eσ=0.1eV and Eσ=0.22eV for 3.06 ML and 3.33 ML samples, respectively.