為了與光積體電路整合並利用低廉的價格製造出適用於可見光、紅外光之光偵測器，一般來說，需要在單晶矽上沉積一層足夠厚且高品質的鍺來實現鍺光偵測器。然而由於矽與鍺的晶格不匹配 (4.2%)，本論文利用低溫氣相沉積方式成功地將30奈米的高濃度矽鍺選擇性沉積在10到20奈米的矽奈米柱上。並利用此結構製作成可見光光偵測器以驗證其特性。 藉由光電性量測得知此矽鍺/矽光電二極體的截止波長為780奈米，暗電流只有10-14安培，最大光電流/暗電流比可以高達4個數量級。此現象表示藉由小面積沉積的方式確實可以得到好的高濃度矽鍺與矽之界面。波長為1500奈米時，在入射光功率只有10微瓦的情況下，元件的光暗電流比依然可高達30倍。由此可知高濃度矽鍺量子點/矽奈米柱光偵測器亦有可能應用於光纖通訊。實驗中也發現到，被矽鍺/矽奈米柱界面所侷限的光電洞會造成轉換電壓的位移，使得電流最低點並非在原點的位置。轉換電壓位移的量與光電流大小有強烈的相依性呈指數關係。因此當元件光響應不明顯時，轉換電壓也提供了另一種判斷截止波長的方法。 For optoelectronic integrated circuit applications, a low-cost, reasonable-performance visible to infrared photodetectors are one of the key component devices. This makes the growth of high-quality, sufficient-quantity Ge on the Si platform in a strong demand. However, it is of challenge in any atomic-layer deposition approach because of the large lattice mismatch (4.2%) between Ge and Si. In this thesis, we selectively deposit high-concentrated SiGe nonocrystals on 10-20-nm-wide silicon nanopillars array in low-pressure chemical vapor deposition technique and demonstrated a significant performance improvement of indium tin oxide (ITO)/Si0.3Ge0.7 quantum dots (QDs)/Si pillar metal/semiconductor (M/S) photodiodes in the dark current reduction and photoresponsivity enhancement for visible to near infrared photodetection. The Si0.3Ge0.7 QDs/Si pillar MS photodiodes exhibit a low dark current of 10-14 A and a photocurrent enhancement of 104, 103 and 30 at the wavelength of 300-800, 1160 and 1500 nm, respectively, whereas no current gain is observed in controlled Si pillars-only (that is, no SiGe QDs) MS diodes. The power-dependent photocurrent analysis shows that the studied Si0.3Ge0.7 QD/Si pillar MS photodiodes have good linearity for incident light power up to 1 mW. A schematic energy band diagram is presented to explain the photo current enhancement in the Si0.3Ge0.7 QDs/Si pillar structure.
