新式鈍化接觸應用於矽基光偵測器之研究;New passivated contact technology development and application for Si-base photodetectors

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Title:	新式鈍化接觸應用於矽基光偵測器之研究;New passivated contact technology development and application for Si-base photodetectors
Authors:	鄧詠鐘;Deng, Yong-Zhong
Contributors:	材料科學與工程研究所
Keywords:	光偵測器;鈍化接觸;矽基;photodetector;passivated contact;silicon based
Date:	2017-07-26
Issue Date:	2017-10-27 13:17:14 (UTC+8)
Publisher:	國立中央大學
Abstract:	傳統上，光電元件透過鈍化層降低表面復合速率，以達到降低元件暗電流之目的，然而金屬與半導體之間並無鈍化層，其載子復合速率較高。為了解決上述問題，有研究團隊提出鈍化接觸技術，以減緩金屬與半導體間的載子復合。此結構為金屬與半導體之間插入超薄的鈍化薄膜，藉由穿隧之方式進行載子傳輸，同時達到良好的鈍化效果。雖然此結構大部分用在太陽能電池上，但太陽能電池結構與光偵測器相似，故本研究將鈍化接觸應用至光偵測器，並探討其元件特性。薄型氧化層為鈍化接觸之關鍵，故本研究先成長不同方式之氧化層，並探討其薄膜特性，而後將氧化層上堆疊氮化矽以提升整體鈍化效果。實驗結果顯示，透過退火溫度為200到800度的快速熱處理，退火溫度為400度時，鈍化接觸可量測到最大載子生命週期為1515us、iVoc為650mV。為了提升此結構之載子傳輸能力，我們利用乾蝕刻減薄氮化矽，使厚度從80nm降至15nm。最後將此鈍化接觸結構應用到矽基光偵測器，實驗結果發現氮化矽與氧化層之鈍化接觸可以使光偵測器暗電流由1.44x10-7 A降低至5.42x10-9 A，暗電流密度最低可達1.93x10-5 mA/cm2。此外亦探討氧化銦錫覆蓋於此鈍化接觸結構，發現可使元件暗電流降至5.36x10-9A ，同時元件於操作偏壓為-5V下響應度具有0.658A/W的表現。 ;Compared with III-V photodetector, Silicon based photodetector has 10 to 100 times higher dark current, so decreasing dark current is an important topic. In the past, Silicon based component reduces the surface recombination rate through the passivation layer to achieve the purpose of reducing the dark current of the component. However, there is no passivation layer between the metal and semiconductor. In order to solve the above problems, A technology call ‘‘passivated contact’’ is proposed to reduce the carrier recombination between the metal and the semiconductor. This structure is inserted the ultra-thin passivation film between the metal and semiconductor, it can achieve a good passivation effect and the carrier can tunnel the passivation. Rencently, this structure is mostly used in solar cells, but the solar cell structure is similar to photodetector, so this propasal of this research is to investigate the passivated contact, and apply it to the silicon based photodetector to lower the dark current density. The ultra-thin oxide layer is the key to passivated contact, so this study first grows the oxide layer in different methods and discusses its properties, and then stacks the silicon nitride on the oxide layer to enhance the overall passivation effect. The experimental results show that Through RTA annealing interval of 200 degrees to 800 degrees to enhance the passivation properties, the passivated contact can measure the maximum lifetime is 1515us, iVoc is 650mV at 400 degrees. In order to enhance the carrier transport capacity of this structure, we use dry etching to reduce the thickness of silicon nitride from 80nm to 15nm. Finally, passivated contact is applied to the silicon-based photodetector. The experimental results show that the passivated contact of the silicon nitride and the oxide layer can reduce the dark current of the photodetector from 1.44x10-7 to 5.42x10-9 A, dark Current density of up to 1.93x10-5 mA/cm2. In addition, it was also investigated that indium tin oxide covered with this passivated contact structure and found that the component dark current was reduced to 5.36x10-9A, and the responsibility of 0.658 A / W at an operating bias of -5 V.
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