Optoelectronic Properties of Free-Standing InGaN Membranes

In this thesis, sacrificial layer is embedded under the 300 nm-thick light emitting diode device with top ITO/Ti/Au thin film deposited on the wafer to protect device. After the electrochemical wet etching, nano-membrane LED are not subject to vertical etching and dramatically increased the lateral etching rate to 250 μm/min. In electrochemical wet etching process, the mechanical stress of ITO/Ti/Au protective layer not only crack the (101 ̅1 ̅) hexagonal pyramid structure but also enhanced the lateral etching rate. In addition to the hexagonal pyramid structure, the surface roughness quite flat (Rms under 2 nm). NM-LED is bending downward direction after lift off. Because MQW is squeezed by lateral lattice, the NM-LED quantum well band is more inclined than ST-LED. The NM-LED PL wavelength is redshift about 1 nm compared with ST-LED. After annealing 600℃ 15 minutes, NM-LED bent downward causing MQW stretched by vertical lattice structure. The PL wavelength of NM-LED blueshift about 2 nm compared with ST-LED. In plane strain extension, PL wavelength is blueshift by changing the amount of deformation. EL of the NM-LED under driving current 0.5 mA, the wavelength redshift about 3.75 nm compared with ST-LED.本論文在300 nm發光二極體元件下埋入一層犧牲層後並在晶圓上成長ITO/Ti/Au薄膜保護奈米薄膜在電化學濕式蝕刻後發光二極體不受到垂直式蝕刻外，並大幅提升蝕刻速度高達250 μm/min並從基板剝離。電化學濕式蝕刻過程中受到Ti/Au保護層的機械應力將(101 ̅1 ̅)六角錐柱體斷裂在表面形成六角錐結構並提升側蝕速率，剝離後的試片除了六角錐外的表面粗糙度相當平整，2×2〖 μm〗^2面積下其Rms為1.76 nm而剝離後的基板的Rms在2 nm以下。剝離後NM-LED彎曲方向朝下，MQW受到上下晶格擠壓造成NM-LED量子井能帶較標準片更加的傾斜PL波長較標準片(ST-LED)紅移了約1 nm，而NM-LED退火600℃15分鐘造成NM-LED彎曲方向朝下MQW受到上下晶格的拉伸PL波長較標準片(ST-LED)藍移了約2 nm。除此之外，在平面拉伸過程中波長隨著體積的改變呈現藍移的現象。ST-LED和NM-LED在0.5 mA電流下電激發光譜峰值458.4 nm較ST-LED波長454.72 nm紅移了約3.75 nm。致謝 I 摘要 II Abstract III 目錄 IV 圖目錄 VI 第一章 序論 1 1-1照明技術的演進 1 1-2半導體發光二極體簡介 3 1-3發光二極體原理 4 1-4壓應力 6 1-5壓電效應( Piezoelectric Field ) 8 第二章 文獻回顧 10 2-1氮化鎵奈米薄膜文獻回顧 10 2-2研究動機 19 第三章 實驗步驟與方法 20 3-1 實驗設計與流程 20 3-2 試片製備流程 20 3-3 雷射處理裝置系統 24 3-4 電化學濕式蝕刻裝置 25 3-5 光學顯微鏡(Optical Microscope, OM) 26 3-6 冷場發射掃描式電子顯微鏡(Field Emission Scanning Electron Microscope, FE-SEM) 26 3-7 電激螢光光譜(Electroluminescence, EL) 27 3-8 光激螢光光譜(Photoluminescence, PL) 28 3-9 原子力顯微鏡 (Atomic Force Microscope, AFM) 29 第四章 實驗結果與討論 30 4-1 氮化鎵奈米薄膜剝離 30 4-2 NM-LED氮化鎵奈米薄膜表面形貌分析 30 4-3 NM-LED之場發掃描式電子顯微鏡(FE-SEM)形貌分析 36 4-4 原子力顯微鏡表面形貌分析 39 4-5 NM-LED薄膜厚度量測 41 4-6 NM-LED應力效應 43 4-7 NM-LED之電激發光光譜量測 50 第五章 結論 53 參考文獻 5