熱退火對砷銻氮化鎵之光學與電學特性的影響

Abstract

本篇論文研究關於砷銻氮化鎵材料在經過熱退火後所造成之光電特性改變。我們對不同熱退火溫度與時間做有系統的研究，並找出最佳的熱退火條件。我們發現雖然熱退火可以去除掉非輻射缺陷，修復晶格結構並且增強光激發螢光強度，卻也會產生受子型的缺陷，同時提高了材料中電洞的密度而使未摻雜的砷銻氮化鎵的電性從N型轉變成P型。從實驗可得知此熱退火後產生的缺陷其活化能範圍在3~4.5 eV之間，極有可能是鎵的空位缺陷(VGa)。我們也發現在熱退火後此材料之光激發螢光(PL)強度增強的同時，會伴隨著放光能隙的藍移。至於此藍移產生的原因，包括氮原子排列的均勻化，帶尾能態的消除或是載子的填充效應。另外，我們也比較了用MBE和RTA兩種熱退火方式，實驗結果說明在MBE的腔體中做熱退火可以有比較好的光激發螢光強度以及光反應度。我們發現在600°C做較長時間的熱退火的材料會比在高溫短時間有更高的光激發螢光強度，以及更少量的放光能量藍移。最後，我們成功的利用N-i-P異質接面的元件結構製作出截止波長超過1600奈米的光偵測器。

This study is about the changes of electronic and optical properties that occur when the dilute nitride GaAsSbN is annealed. In our work, the effect of annealing temperature and duration on the bulk material was systematically investigated, trying to find an optimal annealing condition. Though the thermal treatment annihilates non-radiative centers, restores as-grown defects and enhances photoluminescence (PL) intensities, it induces acceptor-type defects and increases the hole concentrations in the samples, leading to the conduction-type conversion in un-doped GaAsSbN. The formation energy of the defect, determined from Arrhenius plot, is within 2.7~3.8 eV, revealing that the defects could be Ga vacancies. The improvement in PL intensity accompanies with the blue-shift in emission energy. And the origins of this annealing-induced blue-shift in PL peak energy include the homogenization of nitrogen atoms, the reduction in tail states, and the filling effect due to the increment in carrier density. We also compared MBE annealed samples with RTA annealed and the result shows that MBE annealed set can achieve higher PL intensity and better photo responsivity. Finally, we found that annealing at 600°C with longer duration can achieve higher PL intensity and less blue shift than at higher temperatures with shorter duration. At last, we have successfully fabricated GaAsSbN detectors with a cut-off wavelength >1.6 μm.