矽基鍺薄膜光偵測器之研究;Development of Silicon-based Epitaxial Germanium Films and Photodetectors.

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/68637

Title:	矽基鍺薄膜光偵測器之研究;Development of Silicon-based Epitaxial Germanium Films and Photodetectors.
Authors:	陳威旗;Chen,Wei-chi
Contributors:	照明與顯示科技研究所
Keywords:	矽基鍺薄膜;矽基鍺光偵測器
Date:	2015-07-22
Issue Date:	2015-09-23 13:54:13 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究為低溫製備矽基鍺薄膜光偵測器之研究。鍺材料與矽材料相比有較高的載子遷移率，因此鍺材料廣泛應用於高速光電元件，由於能隙為0.66 eV，吸收光之截止波長可達1550 nm，因此適合作為近紅外光偵測器。而矽基鍺薄膜元件，比起鍺晶圓作為基板之元件，有著低成本與易於單石積體化等優點。但是矽與鍺之間存在著4%的晶格不匹配，導致差排缺陷的產生，進而使薄膜品質受影響。國際上許多的團隊皆以高溫(650℃以上)製程或高溫熱退火等方式來解決此問題，高溫雖然可以降低差排缺陷，但是會衍生出矽鍺光偵測器整合在CMOS的溫度限制問題。本研究之光偵測器全程以低溫製程(375℃以下)所製備，此製程之優點可以將矽鍺光偵測器易於整合在CMOS元件上，形成良好的主動元件。本實驗室與”國家奈米元件實驗室”合作利用減壓化學氣象沉積法(RPCVD)在N-type矽基板上低溫製備高品質鍺薄膜，鍺薄膜厚度為500nm與2µm，並利用X光繞射、原子力顯微鏡、蝕刻孔洞密度缺陷法和穿透式電子顯微鏡等進行分析。其中，X光繞射(XRD)量測半高寬為183arsec與119arsec；AFM儀器量測到表面RMS皆約為1nm；蝕刻孔洞密度缺陷法所計算差排缺陷密度(TDD)皆為〖10〗^7 〖cm〗^(-2)，並將高品質矽基鍺薄膜做成光偵測器。本研究矽基鍺光偵測器主要為p-i-n結構，P-type摻雜層製作方法可分為(1) ECR-CVD與(2) 離子佈植，(1)矽基鍺光偵測器主要利用ECR-CVD成長摻雜層在500nm (i-Ge)由RPCVD所沉積的矽基鍺薄膜上，操作偏壓為-1V，可達到低暗電流密度4.34 mA/cm^2(面積大小為530µm×530µm)，並以850nm雷射與1310雷射作為光源，分別獲得0.32A/W與0.24 A/W的響應率(Responsibilty)。(2)在2µm(i-Ge)由RPCVD所沉積的矽基鍺薄膜上，利用離子佈植摻雜硼形成摻雜層，並制備成矽基鍺光偵測器，同樣以850nm雷射與1310雷射作為光源，分別獲得0.05A/W與0.1 A/W的響應率(Responsibilty)；並且有較低的暗電流密度為1.86mA/cm2。離子佈殖摻雜層有很高的載子遷移率與良好的電性，但是我們從二次離子質譜儀(SIMS)圖觀察到表面摻雜濃度不夠，進而無法使半導體與金屬之間形成穿隧接面，且摻雜過深達到200nm，使得此方法製備的光偵測器，其響應率較ECR-CVD法來得低。 ;In this research, topic is Development of silicon-based epitaxial germanium films and photodetectors at a low temperature. Germanium whose bandgap is 0.66eV can absorb near-infrared light of wavelength. Germanium of Mobility is fast than silicon so germanium Integrated in silicon-based generally applies of high frequency device. Due to cutoff wavelength of Ge is at 1550 nm, so germanium can be used as a near-infrared photodetector. Ge films on Si is overcoming the large lattice mismatch (4.2% at 300 K), which cause a high threading dislocation density (TDD) in the Ge layers. Many Group in international use high temperature and annealing in fabrication to solve this problem. High temperature of fabrication will restrict to integrate in CMOS. In this research, all of the manufacture is low temperature(<375℃), advantage of which affect photodetector be integrated in COMS in the future. We cooperated with NDL to operate Reduce Pressure chemical Vapor Deposition (RPCVD).The silicon-based epitaxial germanium Films were manufactured by RPCVD cooperated with NDL. The germanium films are part of 500nm and 2µm which are measured 183arsec and 119arsec by XPD. RMS of germanium films is 1nm by AFM and threading dislocation density is 〖10〗^7 〖cm〗^(-2)by EPD to be a high quality films. The photodetector is p-i-n structure whose way of p-doping are part of 1.ECR-CVD and 2. ion implantation. 1.The photodetector whose germanium films is 500nm by RPCVD are measured dark current density be 4.34 mA/cm^2(area is 530µm×530µm ) at -1V, responsivity is 0.32 A/W in 1310nm of laser and 0.24 A/W in 850nm of laser. 2.The photodetector whose germanium films is 2µm by RPCVD are measured dark current density be 1.86mA/cm^2(area is 530µm×530µm ) at -1V, responsivity is 0.1 A/W in 1310nm of laser and 0.05 A/W in 850nm of laser. Ion implantation of p-doped films possess high mobility and electric conductivity but we know concentration are not enough by SIMS. In this experiment, all of photodetectors have low dark current density. This priority affect device have good signal-noise ratio. Dark current density is often a symptom of poor reliability.
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