臺灣博碩士論文加值系統

本篇論文主要利用光激發螢光光譜（photoluminescence, PL）、X光繞射（XRD）、霍爾量測（Hall measurement）、電解液電場調制反射光譜（electrolyte electro-reflectance, EER）、光電流（Photocurrent, PC）、電晶體特性量測來研究氮化鋁(AlN)插入層對於氮化鋁鎵/氮化镓(AlGaN/GaN)異質結構中二維電子氣（2DEG）所造成的影響以及其相關光電特性。我們分析了兩組樣品，並對於兩組樣品分別做出比較。其中兩組樣品皆使用有機金屬化學氣相沉積法（MOCVD）分別成長在藍寶石基板(第一組)與矽基板(第二組)上。
第一組樣品，根據光激發螢光光譜，以及XRD量測結果來解析各個樣品的鋁成分，分別為22 %、12 %、8 %、12 %在Sample A、B、C和D，接著我們利用調制實驗進一步的確認鋁成分，並發現隨著在表層AlGaN能隙位置隨著逆偏壓的增加有紅移的現象，因此我們認為這是由兩層不同鋁成分之間所形成的量子井所貢獻之訊號，並利用APSYS進行簡單能帶模擬來觀察量子井在逆向偏壓下能隙的變化，最後利用霍爾量測來了解樣品在氮化鋁镓插入層對於樣品在載子濃度以及遷移率的表現。
第二組樣品，分別為Sample A和Sample B，其中Sample A有插入一層氮化鋁在AlGaN/GaN之間，且Sample B擁有較厚的AlGaN。根據光激發螢光光譜，GaN與AlxGa1-xN的訊號可以明顯的被解析出來，其中，Sample A、B中AlxGa1-xN內的鋁成份分別為25.4、25.9 %，從XRD量測結果，我們也計算出與PL量測結果相近的鋁成份，為了深入瞭解存在於AlGaN與GaN接面處的2DEG特性，我們用加偏壓改變樣品內建電場的方式做了電解液電場調制反射光譜與光電流來探討樣品特性。由Fitting過後的EER可計算出Sample A和B中AlGaN層的電場強度，分別為621與430 kV/cm，
我們也從EER實驗發現加入一層氮化鋁間隔層，使2DEG平均位置遠離氮化鋁/氮化镓接面而使接面粗糙散射降低，並由霍爾量測得出Sample A和Sample B的遷移率分別為1367 和 1144 〖cm〗^2 V^(-1) s^(-1)，論文中我們進行了大範圍的霍爾變溫量測，並了解遷移率對於溫度的依賴性，最後我們利用電晶體特性量測了解高溫下兩者其特性。

The optical and electrical characteristisc on three AlxGa1-xN/GaN high electric mobility transistor （HEMT）structures with insertion have been studied using photoluminescence（PL）、XRD、Hall measurement、electrolyte electro-reflectance（EER）、Photocurrent（PC）、Transistor characteristic measurement. We analyzed two groups of samples. And compare for each of the two samples. The two groups of samples used in this study were grown by metal- organic chemical vapor deposition (MOCVD) on SiC and sapphire substrates for two groups Samples.
The First set of samples, We observed the signal of the AlGaN layer to calculate its aluminum composition through PL spectroscopy measurement and XRD. From the PL results, aluminum composition of AlGaN is calculated to be 22%, 12%, 8%, and 12% in samples A B, C, and D respectively. Then we use modulation experiment confirmation of further aluminum components. And found in the surface of AlGaN gap position with increasing reverse bias have red shift phenomenon. So we think this is made up of two layers aluminum components quantum well formed between the contribution of signals. We also performed a simpualion using the Crosslight APSYS software to calculate the bandgap for AlGaN/GaN HEMT. Finally, Hall measurements to understand samples of AlGaN inserted in the sample carrier concentration and mobility performance.
The second set of samples，SampleA and SampleB, respectively. Which Sample A with a insertion layer ALN between AlGaN / GaN and Sample B has a thicker AlGaN layer. We observed the signal of GaN layer and the AlGaN layer to calculate its aluminum composition through PL spectroscopy measurement. From the PL results, aluminum composition of AlGaN is calculated to be 25.4 and 25.9 % in samples A and B, respectively. From XRD data we got the similar compositions. For studying the 2DEG at the interface of AlGaN and GaN, we employed bias-dependent electrolyte electro-reflectance (EER) and bias-dependent photocurrent (PC) to analyze the built-in electric field of AlGaN/GaN heterostructures without and with AlN layer upon the two-dimensional electron channel. Fitting the FKOs yields electric fields of F=621 and 430kV/cm at zero bias for samples A and B, respectively.
We have also added a space layer of aluminum nitride which lets average position of 2DEG leave the interface of AlN/GaN to decrease the interface roughness scattering in EER experiment. Then,we can obtain the mobility in sample A and sample B compared with 1367 and 1144 cm2V-1s-1 from Hall measurement. In this study, we go on a variable temperature Hall measurement, and understand the temperature dependence of the mobility. Finally, we utilize the measurements with the transistor characteristic to find out the characteristic in sample A and sample B in high temperature.

目錄
中文摘要 iii
Abstract v
誌謝 vii
目錄 viii
圖目錄 xii
表目錄 xvi
第一章 緒論 1
1-1 研究背景 1
1-1-1 二維電子氣（two dimensional electron gas, 2DEG） 1
1-1-2 III族氮化物 （III-Nitride） 材料特性 3
1-1-3 AlGaN/GaN HEMT 發展及應用 4
1-2 研究動機 6
1-2-1 AlGaN/GaN HEMTs 元件結構簡介與發展 6
1-2-2 AlN間隔層（spacer layer） 6
1-3 論文架構 8
第二章 氮化鋁鎵/氮化鎵（AlGaN/GaN）極化特性 10
2-1 氮化鎵（GaN）特性 10
2-1-1 為何使用氮化鎵材料 10
2-1-2基板材料 12
2-2 自發性極化效應 13
2-3 壓電極化效應 15
2-4 極化片電荷密度與2DEG片電子濃度 18
2-4-1 極化片電荷密度（sheet charge density） 18
2-4-2 二維電子氣片電子濃度（sheet carrier concentrations） 19
2-4-3 Al成分與AlxGa1-xN厚度對極化電荷、載子濃度影響 20
2-5 樣品結構介紹 26
2-5-1 AlxGa1-xN（/AlN）/GaN HEMT各層之結構 26
2-5-2 樣品結構 28
第三章 量測技術與原理 30
3-1光激發螢光光譜（photoluminescence, PL） 30
3-1-1 光激發螢光光譜原理 30
3-1-2 光激發螢光光譜系統 31
3-2 X光繞射（XRD） 32
3-3 霍爾效應量測（Hall effect measurement） 34
3-3-1 霍爾效應原理（Hall effect measurement） 34
3-3-2 Van der Pauw 量測法 37
3-3-3 霍爾效應量測實驗系統 39
3-4 調制光譜（Modulation spectroscopy） 40
3-4-1 調制光譜原理（Modulation spectroscopy） 40
3-4-2 法蘭茲-開耳希震盪（Franz-Keldysh Oscillation, FKOs） 41
3-4-3 電解液電場調制反射光譜（EER）實驗系統 42
3-5 光電流（photocurrent spectroscopy, PC） 43
3-5-1 光電流光譜相關原理 43
3-5-2 變偏壓光電流光譜實驗系統 44
3-6 高溫電晶體量測 45
3-7 APSYS 46
第四章 結果與討論 47
4-1 光激發螢光光譜 (photoluminescence, PL) 47
4-1-1室溫之光激發螢光光譜 48
4-1-1-1 第一組 樣品 48
4-1-1-2 第二組 樣品 49
4-1-2低溫之光激發螢光光譜 51
4-1-2-1 第一組 樣品 51
4-2光繞射（XRD） 54
4-2-1 第一組 樣品 54
4-2-2 第二組 樣品 56
4-3 霍爾效應量測 （Hall effect measurement） 58
4-3-1 第一組 樣品 58
4-3-2 第二組 樣品 60
4-4電解液電場調制反射光譜（EER） 62
4-4-1 第一組 樣品 63
4-4-2 第二組 樣品 64
4-5 變偏壓光電流光譜（Bias-dependent PC） 67
4-5-1 第一組 樣品 68
4-5-2 第二組 樣品 71
4-6高溫電晶體量測 74
第五章 結論 77
參考文獻 79

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