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標題: | 矽/鍺光偵測器及太陽電池 Si/Ge photodetectors and solar cells |
作者: | Wei-Shuo Ho 何偉碩 |
指導教授: | 劉致為 |
關鍵字: | 紫外光,綠光,紅外光,光偵測器,矽鍺,可撓式,浸沒式離子佈植,表面鈍化,太陽電池, Ultraviolet,Green light,Infrared,Photodetector,Silicon,Germanium,Flexible,Plasma immersion ion implantation,Surface passivation,Solar cell, |
出版年 : | 2012 |
學位: | 博士 |
摘要: | 在本篇論文中,著重在研究矽/鍺穿隧金氧半光偵器以及n型矽基板太陽能電池的元件物理以及光電特性。由於物理極限的限制,半導體產業界將面臨無法跟隨摩爾定律繼續微縮元件尺寸大小,故目前全球的半導體廠商將目標聚焦在如何增加元件的功能以提高半導體晶片的價值。本篇論文研究的矽/鍺金氧半光偵測器以及太陽電池因可與現今製程相容並可應用於生物醫療、光通訊、可撓式電子以及電力供應上,可增加半導體晶片的價值。
在論文的第一部分,主要研究矽與鍺金氧半光偵測器。由於矽可吸收波長小於其截止波長(約為1.1微米)的光子,對於特定頻段的偵測需透過濾光片的搭配或調整接面深度才能達成。為了減少製程複雜度以及降低成本,透過在金氧半結構裡將閘極作為除了訊號讀出的電極外同時也作為濾光片的特性來達成窄頻段的光偵測。由於銀和金的光學特性,當一寬頻譜的光照在以銀和金分別作為閘極的金氧半結構時,銀可濾出紫外光(319nm)而金可濾出綠光(500nm)使其穿透閘極達到下方的半導體層以進一步的吸收,利用此特性製作出紫外光以及綠光的窄頻矽基板金氧半光偵測器。在光通訊的應用上,由於矽無法吸收光通訊波段波長(1.3微米和1.55微米),而鍺的能隙較矽小,可吸收波長1.3微米和1.55微米的光且可和矽製程整合,故鍺是相當具有潛力可應用於光通訊波段的材料。藉由黏合式鍵結及智切的技術,成功將一薄膜單晶鍺轉移到可撓式基板上,提供一種可應用於光通訊波長(850nm,1310nm及1550nm)之可撓式金氧半光偵測器。同時,因為鍺的光吸收係數較矽大,其用於吸收光的材料厚度較薄,更利於撓曲。接著,由於半導體材料表面的缺陷會提供一產生復合機制,使得載子容易透過此缺陷產生或復合,降低了光電元件效能。為了提升光電元件的效能,透過浸沒式電漿離子佈植技術將氫佈植進入氧化層和半導體介面,可將介面缺陷的鈍化。在金氧半光偵測器結構中,經過浸沒式電漿離子佈植技術將缺陷鈍化後,其暗電流下降且光響應度上升。 本論文的第二部分著重研究n型太陽電池的設計、製作與量測。為了有效降低成本,透過降低矽晶圓厚度來減少材料成本是一種有效的方法。然而當厚度減薄時,半導體表面的缺陷復合效應將會主導太陽電池的光電轉換效率。首先,藉由光激發光以及準穩態光電導量測分析了二氧化矽、氧化鋁以及非晶矽在n型及p型基板上的鈍化效果以進行後續應用於太陽電池上。因為n型矽晶圓相較於p型矽晶圓具有較長的載子生命週期,且不會有照光劣化的情形,故未來高效率太陽電池的研究皆著重於研發以n型矽基板來製作太陽能電池。為了在n型基板上製作出p+n接面,一般使用擴散製作表面的p+射極,然而,因為硼在矽中的溶解度低,製程上不易控制,利用在CMOS製程上已相當成熟的離子佈植技術可以克服此問題且其具有可準確控制佈植區域、劑量並可較傳統擴散製程省去硼玻璃移除製程步驟,可以達到高效率n型矽基板太陽電池。 In this dissertation, Si/Ge tunneling metal-oxide-semiconductor (MOS) photodectors and n-type silicon solar cells are investigated. Moore's Law, which holds that the number of transistors on an IC doubles every 18 months. However, due to the physical limitation of CMOS scaling, global semiconductor industry now focusing on a new trend called “More-than-Moore”. By developing novel functions of Si/Ge based devices can add further values to semiconductor chips. Since Si/Ge based MOS photodetectors and solar cells are compatible with current process and have applications on bio-medical, telecommunication, and energy, “More-than-Moore” can be achieved. In the first part of this dissertation, silicon and germanium based photodetectors are investigated. Due to the broad-band absorption of Si with the cut-off wavelength of ~1.1μm, the narrow band detection is difficult for Si-based photodetectors. By using appropriate selection of gate metal, the metal-oxide-semiconductor tunneling diode can detect specific range of light. The gate electrode is not only used for reading out the electronic signal but also used as a filter to select the narrow band photons to enter the Si for further absorption. Si-based photodetectors for narrow-band ultraviolet light (319nm) and green light (500nm) detection are demonstrated. Since Si bandgap (1.12 eV) makes impossible the detection of communication wavelengths at 1310 nm and 1550 nm. With the advantage of compatibility with Si circuitry and the detectability of 1310 nm and 1550 nm wavelength, Ge is a promising detector for telecommunication wavelength. Moreover, due to larger absorption coefficient of Ge as compared with Si, a much thinner active layer is sufficient to detect the photons. The thinner active layer is more suitable for flexible substrates. A flexible Ge-on-polyimide photodetector is demonstrated for telecommunication wavelength. After discussion on the Si/Ge tunneling metal-oxide-semiconductor photodectors, passivation of interface traps at Si/SiO2 by the plasma immersion ion implantation (PIII) of hydrogen is demonstrated. Surface properties of semiconductors might degrade the performance of optoelectronics devices dramatically due to generation and recombination of carriers at surface states. Passivation decreases the dark current and enhances responsivity of metal-oxide-semiconductor tunneling photodetectors. In the second part of this dissertation, the design, fabrication, and measurement of n-type silicon substrate solar cells are investigated. An effective method to reduce cost is to decrease thickness of the wafer. However, surface passivation is becoming vital for thin wafer in order to keep the cell performance. Thermal oxide (SiO2), Al2O3, and a-Si passivation of n-type and p-type CZ silicon wafers are characterized by quasi-steady-state photoconductance and photoluminescence. Finally, Ion implanted boron emitter silicon solar cells were demonstrated. N-type silicon has great potential to achieve high efficiency solar cell due to its superior tolerance of metal contaminations and no light-induced degradation. However, solid solubility of boron is lower than phosphorus. Thus, realization of boron emitter by diffusion on n-type silicon is more complicated than phosphorus emitter on p-type silicon. Ion implantation is a mature technology which has been used in CMOS fabrication for decades and could be a promising method to fabricate boron emitter on n-Si. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/16255 |
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顯示於系所單位: | 電子工程學研究所 |
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