含矽/矽鍺量子井結構發光二極體在不同摻雜濃度下之電激發光特性

Abstract

在本論文中，我們設計了結構為P-I-N及P-P-N接面的矽鍺多層量子井發光二極體，主要探討將量子井結構成長於二極體的空乏區或電子擴散區內對發光頻譜的影響。 經由分析不同溫度下的電激發光頻譜，我們發現P-I-N結構的樣品在低溫時大部份的發光皆來自於量子井結構，至高注入電流時才開始有矽的發光，我們推論在高注入時量子井內的載子數增加可能有助於電洞在矽緩衝層的累積。而P-P-N結構樣品則因矽緩衝層的高摻雜，造成大量電子電洞於緩衝層內復合，不論在低溫或室溫皆有大比例的矽發光。 比較兩樣品的發光效率，我們發現室溫時兩者效率相近，但低溫時P-P-N結構的量子井發光效率較P-I-N結構為高，其可能原因為電子擴散區內的高電洞濃度提升了電子電洞復合率，但室溫時因載子捕捉率下降而使發光趨於飽和。此外我們分析兩樣品量子井發光的溫度響應，並計算不同注入電流下的活化能，我們發現活化能隨著電流上升而下降，而兩樣品在相同注入電流(250mA)下的活化能相差約23meV。

In this thesis we demonstrated 1.3~1.4μm wavelength light emission from 10-period Si/Si0.85Ge0.15 quantum-well (QW) structures. There are two different samples in our investigation: p-i-n and p-p-n structures, grown by UHVCVD system. For the p-i-n sample, the QW structure is in the depletion region of diode, while for the p-p-n sample it is in the electron diffusion region of diode. According to our experiment results, the luminescence of QW dominates and the luminescence of Si is only observed at high bias for p-i-n sample at low temperature. However, the luminescence intensity of QW decreases with temperature because the carriers get more energy to escape the well. For p-p-n sample, the luminescence intensity of Si is enhanced because of the high p-type doping in the Si buffer layer, which causes lots of electron-hole recombination. At room temperature, the efficiency is low for both samples. At low temperature, the efficiency of the p-p-n sample is higher than that of the p-i-n sample. The high hole-concentration in the electron diffusion region (p-type region) may enhance the recombination rate. We also discussed the temperature dependence of the QW luminescence and the activation energy of holes in the well. The activation energy decreases as the current injection increases. The difference in activation energy between these two samples is about 23meV at the same injection condition.