本論文主旨為製作近紅外光之石墨烯-鍺-石墨烯光偵測器(Graphene-Germanium-Graphene photodetector)並加以量測及分析。鍺的吸收波段恰可應用於光通訊常用之近紅外光波長850nm、1310nm與1550nm，一般而言會利用金屬做為光偵測器之電極，但會影響受光面積而造成光損耗。近年來石墨烯常被使用於導電薄膜，其為特殊的二維結構，此類型適合以化學氣相沉積法製備，且非常有潛力應用為透明導電膜，具有很多優異特性及光學穿透率，尤其是在紅外光區幾乎是透明的，我們也藉此提升元件的光電流及響應度。 本研究使用指叉狀電極(Interdigitated electrode)做為光偵測器之電極，其目的是利用簡單的製程做出高頻的元件並應用於IC設計當中。我們利用n-Ge基板做為光偵測器的主動區並以雙層的石墨烯做為電極，而此指叉狀電極是由CVD製備的石墨烯轉印至基板上後利用氧電漿蝕刻圖形，我們入射雷射光於元件區並通以直流電壓量測其光暗電流。以石墨烯作為電極之光偵測器除了能增加照光面積提升光電流亦可增加其光暗電流比而達到整流效果。本實驗鍺基板之光偵測器於850 nm、1310 nm及1550 nm之波長之響應度分別可達0.39 A/W、0.59 A/W及0.77 A/W，其光暗電流比也達三個數量級以上。 ;A graphene-germanium-graphene photodetector (GSG PD) is investigated in this research with transparent graphene electrodes. Germanium is a good absorption coefficient material in near infrared wavelength including 850 nm, 1310 nm and 1550 nm for optics communication. Generally, the metal electrode was utilized for the photodetector applications. However, there were a lot of light loss for the non-transparency. In recent years, graphene has been found to be a good transparent conductive film (TCF) with a two-dimensional monolayer composed by sp2-bonded carbon atoms. Due to its exceptional electrical conductivity and high optical transmittance especially including near infrared, graphene is one of the promising candidates for TCFs. Therefore, the higher photo-current and responsivity of the device with graphene can be achieved. In this investigation, interdigitated graphene electrodes were applied to a near infrared photodetector. We used a n-type germanium as the substrates and graphene layers as the interdigitated electrodes of the photodetector. The interdigitated graphene electrodes were prepared by chemical vapor deposition (CVD), and transferred to the substrate first, then patterned by O2 plasma. The responsivity of the n-Ge PD was 0.39 A/W, 0.59 A/W and 0.77 A/W for the wavelength 850 nm, 1310 nm and 1550 nm of the incident light, separately. And the photo to dark current ratio was over three orders.
