可見光/紅外光偵測器技術之研究

Abstract

自十九世紀紅外光被發現後，紅外光偵測技術就開始不斷被研究，時至今日，紅外光已廣泛被應用於軍事、商業、學術和生活等領域，看好光譜儀裝置未來應用於隨身檢測的潛力，因此本論文專攻於其中不可或缺的光偵測器模組。 本論文中嘗試了兩種製作光偵測器的方法。首先，以石墨烯薄膜製作光偵測器，於具有轉移石墨烯薄膜的矽基板表面以微影製程製作電極和擋光層結構，製成石墨烯光偵測器，並以鎖相放大器量測微弱光電流訊號，並嘗試與量測中以外加偏壓加強光電流訊號。另一則是以蕭特基能障二極體元件作為光偵測器，先後以n型和p型矽基板製作蕭特基能障二極體元件，使用金(Au)與n型矽基板形成蕭特基接面，製作蕭特基能障二極體元件，量測發現可藉由半導體能隙吸收偵測能量大於矽能隙之光子。接著使用銅(Cu)與p型矽基板形成能障更小的蕭特基能障二極體，經量測發現，銅/p型矽蕭特基能障二極體元件，透過內部光激發吸收機制，可偵測到1.55微米的光通訊波段光子訊號，產生光電流訊號。 本論文中成功以石墨烯和矽之蕭特基能障二極體元件製作光偵測器，並架設系統或透過儀器量測，確認其光偵測能力，石墨烯和矽之蕭特基能障二極體元件都可確實偵測可見光訊號，其中銅/p型矽蕭特基能障二極體元件甚至可偵測到波長1.55微米的光子訊號，達成能隙下吸收(below band gap absorption)。

Since the presence of infrared light was first discovered in the 19th century, the development of infrared light detection technology has never been stopped. Nowadays, infrared technology has been applied to military, business, scholarship and regular life. Being optimistic to the potential of portable spectrometer in the future, this thesis focuses on studying the photodetector module which is an indispensable of the portable spectrometers. In this thesis, two main methods of fabricating photodetector are studied. The first one is using graphene to build a photodetector. To build the graphene photodetector, a graphene film is transferred onto the silicon substrate with oxidation layer, and then the metal electrode and shadow layer is built upon the graphene film. The lock-in amplifier is used to measure the weak photocurrent signal of graphene photodetector. Further, the photocurrent is found that can be enhanced by the bias voltage. The other studied method is Schottky barrier diode, which can divide the generated electron-hole pair with the Schottky barrier. Au/n-type Si Schottky barrier diode is studied first and it’s found that the Au/n-type Si Schottky barrier diode can detect the photons with energy higher than silicon band gap. The Cu/p-type silicon Si Schottky barrier diode is then fabricated to achieve smaller Schottky barrier height. Within the photo-detection measurement, the Cu/p-type silicon Si Schottky barrier diode can detect the 1.55μm photons and generate the photocurrent signal through internal photoemission absorption. Both the graphene photodetecctor and silicon Schottky barrier diode are successfully fabricated in this thesis and their detection ability are also verified by measurements. Graphene photodetecctor and silicon Schottky barrier diode can exactly detect the visible photons. Especially, the Cu/p-type silicon Si Schottky barrier diode can detect the 1.55μm photons whose energy is below silicon band gap.