操作於1350至1700 nm光波段之高性能鍺錫光二極體

GeSn-based photodiode with high performance operated from 1350 to 1700 nm

林浩晟(Hao-Cheng Lin)

指導教授 ： 鄭鴻祥

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201802333

摘要

近年來，許多學者研究鍺錫光二極體並廣泛應用於光通訊與紅外光影像焦平面陣列系統，透過錫的加入可以改變鍺的能帶結構，當錫濃度達特定量時，鍺錫合金會轉變為直接能隙能帶結構，作為光偵測器時可以延長光吸收波段。在本論文中，我們使用分子束磊晶系統將p型鍺/鍺錫異質結構成長於n型鍺基板上，並製作成 p-i-n結構光二極體，我們將會分析SiO2表面鈍化光二極體各項參數，其中包含表面與基材漏電流密度分析，在低溫量測中(220 K至300 K)，探討光二極體漏電流的產生機制，以及分析各項雜訊電流的組成成份。接著我們將詳細描述SiO2與SiO2/GeO2兩種不同表面鈍化技術製作之鍺錫光二極體，利用熱氧化的方式在元件表面形成二氧化鍺薄膜，可以有效的抑制表面漏電流的產生，並且分析二氧化鍺氧化層對於光二極體的光響應率、外部量子效率、雜訊電流與光感測度的影響，在光正向入射至樣品表面的情形下，計算空氣/氧化層及氧化層/p型鍺介面造成的光反射與p型鍺的光吸收，由此驗證實驗數據的合理性。
在未來，我們需要最佳化表面鈍化之技術，製作出具高性能與兼容性的鍺錫光二極體，更可與其他光電元件同時整合至矽基板上，成為積體光學電路的主軸。

關鍵字

鍺錫光二極體 ； 光偵測器分子束磊晶 ； 二氧化鍺 ； 表面鈍化技術

並列摘要

In recent years, many researchers study GeSn photodiodes that were applied optical communication and focal plane array infrared imaging system. The incorporation of Sn into Ge can adjust bandgap structure of Ge. When Sn content increases over specific amount, GeSn alloy transfers indirect bandgap into direct bandgap. Therefore, GeSn photodetector can extend light absorption spectrum. In this work, we successfully grew the p-type Ge/GeSn layers on n-type Ge wafer using the MBE system and fabricated into the p-i-n photodiodes. We analyzed the parameters of the SiO2 surface passivated photodiodes which the surface and bulk leakage current density were included in. In low-temperature measurement (220 K to 300 K), we investigated what the generation mechanism of leakage current of the photodiodes is. In addition, the various components of noise current were observed. Then, we exceedingly explain the capability of GeSn photodiodes of SiO2 and SiO2/GeO2 surface passivation. The way used rapid thermal oxidation grew GeO2 film on surface of device, preventing the generation of surface leakage current efficiently. Moreover, it is showed that being added GeO2 layer influence the responsivity, external quantum efficiency, noise current and specific detectivity in diodes. Under front-side illumination, we calculated the reflection of air/oxide and oxide/p-type Ge interface as well as the absorption of p-type Ge, confirming the reasonability of experimental results.
In the future, we need to make the optimization of surface passivation technique in order to fabricate the GeSn photodiodes with high performance and compatible. More, it can be integrated with group-Ⅳ photonics on the Si substrate at the same time, which is one of the main issue of integrated optical circuit.

並列關鍵字

GeSn photodiode ； photodetector ； molecular beam epitaxy ； GeO2 ； surface passivation

參考文獻

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[2]https://warwick.ac.uk/fac/sci/physics/current/postgraduate/regs/mpagswarwick

/ex5/intro/elemental/

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