量身訂作鍺量子點崁入式發射器與鍺量子點光偵測器應用於單石積體化矽光電晶片;Designer Ge-dots embedded emitters and Ge-dots photodetector for monolithically-integrated Si optical interconnects

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Title:	量身訂作鍺量子點崁入式發射器與鍺量子點光偵測器應用於單石積體化矽光電晶片;Designer Ge-dots embedded emitters and Ge-dots photodetector for monolithically-integrated Si optical interconnects
Authors:	郭銘浩;Kuo, Ming-Hao
Contributors:	電機工程學系
Keywords:	鍺量子點;光傳輸;光偵測器;光發射器;光電晶體;Ge QD-dots;optical interconnects;photodetectors;photo emitters;phototransistors
Date:	2018-01-26
Issue Date:	2018-04-13 11:24:20 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文展示了精確控制鍺量子點Si3N4或SiO2中之位置和數量的能力。藉由選擇性氧化氮化矽與二氧化矽上方之矽鍺納米柱之技術，以“量身訂作”鍺量子點掩埋於矽基版上之氮化矽與二氧化矽之中。藉此，我們成功地製作了不同種類的鍺量子點光電元件，如鍺量子點嵌入式光發射器和鍺量子點金氧半光電晶體，為光互連和通信系統應用提供了一種可行途徑。將嵌入二氧化矽中的30-70nm 鍺量子點整合於微碟盤中 (microdisk)。藉由拉曼波峰紅移證明，當嵌入二氧化矽中的鍺量子點隨著尺寸愈小而受到量子侷限效應和拉伸應力愈大。如此大的量子限制效應和拉伸應變效應，造成價電帶會分裂為輕空穴價電帶 (LH) 與重空穴價電帶 (HH)，使得螢光光激發譜線上解析出0.83eV (LH) 和0.88eV (HH) 之兩個波峰。測量由10 K到100 K之時間解析螢光光激發譜線，觀察出對溫度不敏感的光激發載子的生命週期分別為2.7ns (HH) 和5ns (LH)。藉此，分別為拉伸應變之鍺量子點提供了直接帶隙光致發光的更強有力證據。最後，我們提出了一種新『一體成型』SiO2 / Ge-dot / SiO2 / SiGe異質結構為本，運用CMOS技術，製作出應用於能夠偵測可見光至近紅外光之鍺量子點光電晶體。其中，閘極氧化層厚度和鍺量子點的直徑都是可調變的。當鍺量子點光電晶體操作於ON區和OFF區下，分別可以藉助鍺量子點引發的光伏和光導效應，來增進光電晶體在400-1550nm波長區間的光響應度、光電流增益、以及操作速度。對於將鍺量子點體積歸一化，解析出隨著將閘極氧化層厚度從38.5nm降低到3.5nm、鍺量子點直徑從90nm降低到50nm，鍺量子點光電晶體之光電轉換效率和響應速度都得到顯著改善。其中在90nm鍺量子點光電晶體在入射光波長為 850nm 和 1550nm (目前光通訊波段主流) 10nW的照射下，都展現極高的光響應度，分別為 1.210^4 A/W和300 A/W。尤其在溝道長度為3微米的50nm鍺量子點光電晶體，在850nm脈衝雷射照射條件下，元件響應時間為0.48ns，3dB頻率達到2GHz，這為未來矽基光互連提供了巨大的潛力應用。 ;This thesis demonstrates the capability of precise control of locations and numbers of Ge QDs within Si3N4 or SiO2. Based on the “designer” Ge nanodots in Si3N4 and SiO2 matrix on Si substrate through high-temperature selective thermal oxidation of SiGe nanopillars-on-insulator such as silicon nitride and silicon oxide over Si substrate. We have successfully reported different kind of Ge nanodots photonic devices, such as Ge nanodots embedded emitters and Ge QD MOS phototransistor, providing a way for optical interconnect and communication system applications. We incorporated 30－70nm Ge nanodots embedded within SiO2 into a microdisk. The Ge nanodots embedded in SiO2 are subjected to increasing quantum-confinement and tensile-strain by reducing dot size, as evidenced by large Raman red shifts. These large quantum-confinement effect and tensile-strain effect are consistent with the strain-split photoluminescence transitions to the light-hole (LH) and heavy-hole (HH) valence bands at 0.83eV and 0.88eV, respectively. Time-resolved photoluminescence measurements conducted from 10-100 K show temperature-insensitive carrier lifetimes of 2.7ns and 5ns for the HH and LH valence-band transitions, respectively, providing additional strong evidence of direct bandgap photoluminescence for tensile-strained Ge nanodots. Finally, we report a novel visible-near infrared photoMOSFET containing a self-organized, gate-stacking heterostructure of SiO2/Ge-dot/SiO2/SiGe-channel on Si substrate that is simultaneously fabricated in a single oxidation step. Both the gate oxide thickness and the diameter of the Ge dots are controllable. Large photocurrent enhancement was achieved for our Ge-dot photoMOSFETs when electrically-biased at ON- and OFF-states based on the Ge dot mediating photovoltaic and photoconductive effects, respectively. Both photoelectric conversion efficiency and response speed are significantly improved by reducing the gate-oxide thickness from 38.5 nm to 3.5 nm, and by decreasing Ge-dot size from 90 nm to 50 nm for a given areal density of Ge dots. Photoresponsivity (R) values as high as 1.210^4 A/W and 300 A/W are measured for 10 nW illumination at 850 nm and 1550 nm, respectively. A response time of 0.48 ns and a 3 dB-frequency of 2 GHz were achieved for 50 nm-Ge-dot photoMOSFETs with channel lengths of 3um under pulsed 850 nm illumination, offering a great potential for future Si-based optical interconnection applications.
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