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標題: | 共振腔發光電晶體之研製與分析 Fabrication and Characterization of Resonant-Cavity Light-Emitting Transistors |
作者: | Wen-Chiung Tu 涂文瓊 |
指導教授: | 吳肇欣(Chao-Hsin Wu) |
關鍵字: | 電晶體,發光電晶體,共振腔,穿隧接面, Resonant-Cavity,Light-Emitting Transistors,Tunnel Junction,HBT, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 本篇論文的主要研究為具共振腔發光電晶體的製程與其元件特性量測與分析。電晶體的基極為元件之主動區,其中包含了兩個In0.2Ga0.8As的量子井用以增強放光效率。元件結構為利用Al0.12Ga0.88As/Al0.9Ga0.1As的布拉格反射鏡當作上下反射層,其中下層對數為35,上層對數為3,使光能在共振腔中形成共振,進而增加元件的發光強度。因此相較於一般發光電晶體自發性放光的半高寬(≈ 96 nm),布拉格反射鏡結構可以使得半高寬達到7.3 nm。此外透過製程的方法,使上方的反射層減少為1對,觀察此兩種不同共振腔發光電晶體的放光能力、放光頻譜以及光調變頻率的影響。我們在共振腔發光電晶體的基-集極接面為高參雜濃度形成的穿隧接面,使得電壓控制光的調變能力增強,和一般發光電晶體由電流控制有所不同。更進一步,藉由穿隧效應使得光的調變速度達到1.31GHz,比一般共振腔發光電晶體的0.4 GHz還快上許多。因此,除了透過共振腔得到更小的光譜線寬以外,再加上穿隧效應使得光的調變速度變快,共振腔發光電晶體能更因應未來短程光通訊系統之市場。最後我們還比較了不同磊晶結構的穿隧接面對元件電流電壓訊號的影響,其中對穿隧機率較大的元件來說,操作在飽和區或順向主動區時,固定基極電流的輸入會無法得到一放大固定的集極電流,集極電流反而是隨著電壓提高而劇烈上升。換言之,穿隧電流為集極電流主要來源,進而影響其電流-電壓特性曲線。
此外,我們還探討了InGaP/GaAs發光電晶體的熱效應,並和傳統異質接面雙極性電晶體比較。發現了當溫度升高時,傳統電晶體的電流增益會下降,然而發光電晶體卻有相反的趨勢,而且對溫度的變化十分敏感。例如到從室溫到85°C,發光電晶體之電流增益增加了76.77%,傳統電晶體則是下降7.96%。同時藉由分析載子在基極量子井區域中動態分布和傳輸狀態,未來可以設計發光電晶體應用在熱感應溫度計上。 This thesis presents the fabrication and characterization of resonant-cavity light emitting transistors (RCLETs). The base layer, which is the active layer, includes two undoped In0.2Ga0.8As quantum wells to enhance the base radiative recombination. With 35 pairs of bottom Al0.12Ga0.88As/Al0.9Ga0.1As Distributed Bragg Reflector (DBR) and 3 pairs of top DBR sandwiching LET structure, the spontaneous emission properties from a light-emitting region located inside the resonant cavity are enhanced by the resonant-cavity effect. The full width at half maximum (FWHM) of emission peak of RCLET is 7.3 nm at 972nm while that of conventional LET is 96 nm. In addition, devices with different upper DBR pairs are fabricated and compared. The optical output of RCLETs with a tunnel junction collector is sensitive to the voltage change of the collector terminal owing to base-collector tunneling phenomenon, which is differ from the current modulation of conventional LETs. Furthermore, as compared with conventional RCLETs with response bandwidth of 0.4GHz, the response bandwidth can be pushed to 1.31GHz by incorporating a tunnel junction. Therefore, the RCLET with a tunnel junction shows a great potential for commercial short distance communication system. We also investigate the characteristics of different tunnel junction layer designs. If the tunneling probability is larger, the collector current will increase rapidly with bias voltage in the forward-active mode or saturation mode. In other words, the tunnel current dominates the whole collector current and affects the I-V characteristics. Moreover, we investigate the temperature effects on transistor current gain between InGaP/GaAs LETs and heterojunction bipolar transistors. We demonstrate the enhancement of the current gain of 76.77% from room temperature to 85°C. On the contrary, the conventional HBT shows a decrease of current gain of 7.96% at high temperature. The unique current gain enhancement in LETs is due to escape of carriers from quantum wells in the base region. A simple thermionic model is used to explain the experimental data. The sensitive temperature characteristics of current gain make the LET as a potential sensitive temperature sensor. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/61629 |
全文授權: | 有償授權 |
顯示於系所單位: | 光電工程學研究所 |
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