邊射型電晶體雷射內部損耗的特性分析

本篇論文主要研究動機為不同共振腔鍍膜條件的邊射型電晶體雷射研製，以及上述不同元件在室溫(凱氏溫度298 K)和低溫(凱氏溫度82 K)操作下的電訊號和光訊號特性。本實驗所製作的電晶體雷射，是以砷化鎵為基極主要材料，並置入In0.2Ga0.8As量子井作為發光主動層，與上方射極和下方集極的AlGaAs披覆層形成優良的光場侷限波導結構。利用傳統黃光製程和半導體蝕刻等技術製作邊射型放光元件，再進行共振腔端面鍍膜。本次實驗共有三種不同鍍膜條件，分別為：第一種是雷射共振腔一邊鍍上高反射膜，另一端面鍍上抗反射膜。第二種是雷射兩端面皆鍍上高反射膜，最後一種是雷射共振腔兩端皆未鍍膜，為自然砷化鎵劈切斷裂鏡面所形成的共振腔。不同元件在室溫量測下，元件皆為自發性放光，而在基極電流為24 mA且較大的集極對射極偏壓下，電流增益是大於1的，且因為鍍膜條件的不同會有不同的電流增益和發光特性，甚至會導致集極電流崩潰的現象發生，這與元件基極－集極接面逆偏時的「法蘭茲－凱爾迪西光子吸收效應」有關，發光頻譜也會因為鍍膜而半高寬會有變小的趨勢。在把元件降至低溫後，因閥值載子濃度下降以及內部損耗的減少，使元件因受激放光產生同調雷射光源，並比較差異性較大的兩種不同鍍膜元件，並分析載子在基極區復合速度的快慢，可以發現到受激放光復合速度比自發性放光時快了2.05倍，且鍍膜後的元件也比未鍍膜元件還要快上1.39倍。在頻譜部分，我們發現到元件在高基極電流注入的情況下，是為單模雷射光，且半高寬約為0.5 nm。在論文最後，根據室溫和低溫下的實驗結果，我們分析了在室溫和低溫下不同基極－集極接面逆偏條件下「法蘭茲－凱爾迪西光子吸收效應」所產生的內部損耗，並得到在基極－集極接面逆偏增加時，內部損耗會跟著增加，使得雷射整體損耗上升，雷射的閥值電流也會跟著增加，在此我們也為電晶體雷射定義了新的參數「等效內部損耗」。在本文最後我們定量地列出所有分析數值提供讀者作為參考。

關鍵字

電晶體雷射；法蘭茲－凱爾迪西光子吸收效應；鍍膜；內部損耗

並列摘要

This thesis presents the fabrication and characterization of edge-emitting transistor lasers (EETLs). We measure the electrical and optical signal of the devices under room temperature (Kelvin Temp. 298 K) and low temperature (Kelvin Temp. 82 K). The structures of the devices in the experiment employ GaAs as the base material, and incorporate In0.2Ga0.8As quantum well as the active region for radiative recombination. After we finish device process, we coat dielectric mirrors on the cleaved laser facets with different coating conditions: the first type of device with one side high-reflection and the other side anti-reflection; the second one with both sides anti-reflection; the third one with both sides uncoated. The measurement at room temperature shows that all devices with different coating conditions have the current gain larger than 1 when they operate at high base current and collector-to-emitter voltage. With different coating conditions, the devices show great differences on electrical and optical signals due to different Franz-Keldysh photon absorption effects happening at base-to-collector junction, varied by different photon confinement in the laser cavity. In addition, the optical spectrum will change because of the different coating conditions on each device. The measurement at low temperature shows that not only the threshold carrier concentration will decrease but also internal loss, so the devices can operate under stimulated emission. We also compare the base recombination lifetime between different devices and conditions. We observe that the device with high-reflection coating on the two cavity facets has faster base recombination lifetime than the device without coating. Finally, we analyze the internal loss of edge-emitting transistor lasers and define a new parameter called "effective internal loss" for transistor lasers. The effective internal loss considers the conventional losses in a light-emitter as well as the unique Franz-Keldysh absorption, which is a function of bias and photon energy. We list all calculated parameters of the transistor lasers in the end for future design of better performance transistor lasers.

並列關鍵字

Transistor lasers ； Franz-Keldysh photon absorption effect ； Coating ； Internal loss

參考文獻

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邊射型電晶體雷射內部損耗的特性分析

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