| 摘要: | 本論文使用選擇性熱氧化複晶矽鍺柱形成高品質之單晶鍺量子點，並將鍺量子點作為有效的光吸收層，成功製備出不同本質層厚度的P-I (鍺量子點) -N近紅外線光偵測器。藉由不同大小之鍺量子點陣列整合於複晶矽/鍺量子點/單晶矽異質接面之 P-I-N光偵測器二極體架構中，我們在近紅外光的波段下可觀察到光響應。在850 nm、980 nm、 1310 nm 及 1570 nm之雷射光源於2.5 mW的照射下，元件得到的光電流與暗電流比值最高為28、15、2.3以及1.6倍。在近紅外光線照射下，鍺量子點/矽界面所侷限之正電荷造成內建電場的產生，使得元件在操作速度上最快可達到440 MHz之操作頻率。
本文另一主題是以UHV-CVD沉積約1 μm厚堆疊式偶合矽/鍺量子點堆疊結構，來製備近紅外線光偵測器。評估在單一偶合量子點中，增加矽/鍺量子點接面數目的設計，對於光響應之影響。於850 nm、980 nm、1310 nm 及1570 nm 的雷射光源於照射下，其元件所展現之光電流與暗電流比值最高為4000 (0.45 mW)、2200 (0.45 mW)、52 (9.4 mW) 與 4.2 (5.4 mW) 倍。隨著單位元下矽/鍺量子點異質接面的數目增加，可清楚地觀察到元件之開路電壓會隨接面數目增加而變大，因此證明了矽/鍺接面數目越多，內建電場也隨之增強，有利於光響應的增進。
;This thesis produced high-quality and single-crystal Ge quantum dots (QDs) using selectively oxidation of SiGe pillars, and demonstrated Ge-QD P-I-N near-infrared photodetectors with various sizes of Ge QD. The P-I-N photodetectors exhibit various near-infrared photoresponsivities by tuning different sizes of Ge-QD arrays integrated in the photodetectors. Under 2.5 mW illumination at 850, 980, 1310, and 1570 nm, the photodetectors exhibit the photo-current-to-dark-current ratio as high as 28, 15, 2.3, and 1.6, respectively. Under near-infrared illumination, the positive holes confined in the valance band offset between Ge QD and the Si substrate, establishing a built-in electric field (E-field), leading the transient response of the photodetectors as high as 440 MHz.
The other topic of this thesis focused the formation of near-infrared photodetectors with a 1-μm-thick Ge QD/Si heterojunction contained various number of Ge QD/Si stacks by using Ultra-High Vacuum Chemical Vapor Deposition (UHV-CVD), and investigated the photoresponsivity of the photodetectors affected by the number of Ge QD/Si stacks. The photo-current-to-dark-current ratio of the photodetectors is 4000 (0.45 mW), 2200 (0.45 mW), 52 (9.4 mW), and 4.2 (5.4 mW) under illumination at 850, 980, 1310, and 1570 nm, respectively. The open-circuit voltage increases with the number of heterojunction of Ge QD/Si, which indicates the increasing built-in E-field improves the photoresponsivity. |
