低暗電流、高響應度、及均勻光敏特性之磷化銦/砷化銦鎵系列短波紅外光偵測器

Low Dark Current, High Responsivity, and Uniform Photosensitivity of InP/InGaAs PIN Short-Wavelength-Infrared Photodiodes

李岳霖(Yueh-Lin Lee)

指導教授 ： 吳孟奇 ； 何充隆

國立清華大學/電機資訊學院/光電工程研究所/博士(2014年)

摘要

於本論文中，我們設計與製作平面型大面積之磷化銦/砷化銦鎵系列異質接面光偵測器元件，並結合不同抗反射層和二次吸收路徑反射結構，以增進元件之響應度、量子效率、及光敏特性。其中，抗反射層結構是由高低折射係數材料所組成，分別包括絕緣型氧化矽/氮化矽雙層、導電型氧化矽/氧化鎵鋅雙層、及導電型氧化矽/氧化鎵鋅/氧化鎳三層結構。而二次路徑反射結構則由金鍺合金所構成。
　為了製備n型氧化鎵鋅導電薄膜，我們採用化學氣相沉積相關之熱模式與電漿模式原子層沉積技術，以及物理氣相沉積機制之射頻濺鍍法等沉積方式。就原子層沉積技術而言，是以一層一層成長方式來形成三明治多層結構的氧化鎵鋅薄膜，且可藉由調變成長溫度和導入不同氧來源，以改善此薄膜特性。如此，可獲得3.8 x 10-3 Ω-cm的電阻率和3.4 x 1020 cm-3的載子濃度，並在可見光與紅外光範圍可得到高於90%的平均穿透率。就射頻濺鍍技術而言，其製備的氧化鎵鋅薄膜可得到2.9 x 10-3 Ω-cm的電阻率和3.6 x 1020 cm-3的載子濃度，然而，過低的光學穿透率使得它無法應用於短波長紅外光區域範圍。另一方面，p型氧化鎳導電薄膜可藉由電子束蒸鍍法並搭配氧氣環境的快速退火方式來製作完成。
　而利用射頻濺鍍與原子層沉積兩種技術，成長重摻雜的氧化鎵鋅薄膜於p型磷化銦/砷化銦鎵的結構上，其呈現出蕭特基接觸之特性，而此n型氧化鎵鋅/p型磷化銦接面存在之能障，能藉由二次鋅擴散步驟與採用氧化鎳嵌入層來降低能障高度，使之呈現歐姆接觸特性。經由二次快速熱鋅擴散製程，在p型磷化銦層之表面可得到高的鋅原子濃度(5-8 × 1018 cm-3)。為了探討其接觸特性表現，在p型磷化銦層上設計並建構一系列傳輸線法之結構，此外，由於接面能障高度扮演著一關鍵因素，可藉由導入氧化鎳嵌入層於n型氧化鎵鋅和p型磷化銦接面之間，以達到歐姆接觸特性。而金/鉻/氧化鎵鋅/氧化鎳接觸結構建立於鋅摻雜之p型磷化銦層上，在經過430℃時間180 sec的熱退火處理後，可獲得良好的歐姆接觸行為，以及3.07 × 10-4 Ω-cm2的特徵接觸電阻。如此，若在元件應用上，利用電漿模式原子層沉積技術成長透明導電的氧化鎵鋅層於磷化銦/砷化銦鎵系列光二極體，可有效改善元件之橫向電阻的問題，除此之外，氧化鎳層能進一步降低n型氧化鎵鋅和p型磷化銦接面之間的能障高度，達到元件優化的目的。
　氧化矽/氧化鎵鋅/氧化鎳三層抗反射結構呈現90%以上之平均光學穿透率及低於10%以下之反射率，而金鍺/金合金之背面反射鏡可呈現80%以上的光學反射率，如此，結合抗反射鍍膜層和二次路徑反射結構此兩項優點，可達到減少入射光的損耗與增加二次光學路徑的吸收，以此提升元件表現。藉由導入透明導電型抗反射層和二次路徑反射鏡，至平面型大面積之磷化銦/砷化銦鎵系列光偵測器元件之結構中，其元件可呈現的低暗電流密度為32.8 nA/cm2於-5 V偏壓下、高崩潰電壓達到-35V、內建電位約為1.65 eV，在1310 nm和1550 nm波長的光照射之下，可得到高的光響應度分別為0.93 A/W和1.09 A/W，且在1000 nm至1600 nm波長頻譜下，其高量子效率接近90%，截止波長大約落於1650 nm波長。搭配SiO2/GZO/NiOx導電型抗反射結構的光偵測器元件，以相對較高能量的光照射在不同元件吸光位置之下，其可呈現均勻的光敏性分布。

關鍵字

磷化銦/砷化銦鎵 ； 響應度 ； 量子效率 ； 光敏特性 ； 氧化鎵鋅 ； 原子層沉積 ； 射頻濺鍍法 ； 氧化鎳 ； 蕭特基能障高度 ； 歐姆接觸 ； 透明導電型抗反射層

並列摘要

In this dissertation, we report on the design of large-area planar InP/InGaAs/InP heterostructure p-i-n photodiodes (PIN-PDs) with various antireflective layer structures and double-path reflectors for the enhancement in the position sensitivity, device response, and quantum efficiency. The antireflection (AR) coating structure is composed of high and low refractive index materials, including the insulating type of SiO2/Si3N4 bi-layer, conducting type of SiO2/GZO bi-layer, and conducting type of SiO2/GZO/NiOx tri-layer. The double-path reflector consists of AuGe-based alloys.
　The thermal-mode ALD (TM-ALD), plasma-mode ALD (PM-ALD), and radio-frequency (RF) sputtering methods were employed to deposit the n-type conductivity of GZO films. For ALD technology, a sandwich structure of GZO films was accomplished by layer-by-layer growth method. The performance of GZO films can be improved by modulating the growth temperature and introducing various oxygen sources. ALD-GZO films exhibit a resistivity of 3.8 x 10-3 Ω-cm, carrier concentration of 3.4 x 1020 cm-3, average optical transmittance of above 90% in the visible and infrared regions. For RF-sputtering, GZO films exhibit the resistivity of 2.9 x 10-3 Ω-cm and carrier concentration of 3.6 x 1020 cm-3. However, the optical transmittance is too low to be used for the infrared regions. On the other hand, the p-type conductivity of NiOx film can be fabricated by both e-beam evaporation and RTA process in oxygen ambient.
　Thus, the heavily GZO films (＞1020 cm-3) with low resistivity (~10-3 Ω-cm) were deposited onto the p-InP/InGaAs structure by both RF sputtering and PM-ALD, which always reveal a Schottky contact characteristics. The barrier height improvement at the n-GZO/p-InP interface is proposed by using the dual zinc driven-in steps and a NiOx insertion layer to realize the ohmic characteristics. The high zinc concentration (5-8 × 1018 cm-3) is first obtained in the surface of p-InP cap layer via the dual zinc driven-in steps. An array of transmission line method (TLM) structures were designed and constructed on top of the p-InP cap layer for the contact performance. The barrier height plays an important role for the formation of ohmic property between n-type GZO and p-type InP using NiOx insertion. By inserting a NiOx layer between GZO and Au/Cr contact films, the Au/Cr/GZO/NiOx contact pad for zinc driven-in p-InP cap layer exhibits a good ohmic contact behavior and a low specific contact resistance of 3.07 × 10-4 Ω-cm2 with the post-annealing process of 430℃ for 180 sec. Thus, the transparent conducting Ga-doped ZnO (GZO) layer was grown on top of the InGaAs PIN-PDs by PM-ALD to improve in the lateral resistance effect, and the NiOx layer was used to reduce the barrier height between n-GZO and p-InP.
　The SiO2/GZO/NiOx antireflection shows an average optical transmittance of above 90% and reflectance of below 10% in the infrared spectrum. The AuGe/Au backside reflector presents the optical reflectance of above 80%. Then, the combination of two features of antireflection coating and double-path reflector is employed to decrease incident-light loss and increase double-path absorption. By introducing both the transparent-conducting-based AR coating and double-path reflectors into the device structure, the large-area planar InGaAs PIN-PDs exhibit a low dark current density of 32.8 nA/cm2 at 5-V reverse bias, a high breakdown voltage of 35-V reverse bias, high build-in voltage of 1.65 eV, high responsivity of 0.93 A/W at 1310 nm and 1.09 A/W at 1550 nm, and a high quantum efficiency of near 90% in the 1000-1600 nm spectral range. The cutoff wavelength is obtained to be about 1650 nm. Under the high-power light illumination, the photosensitivity profile of position information of InGaAs-based PD with SiO2/GZO/NiOx AR coating tri-layer is uniform and instantaneous distribution.

並列關鍵字

InP/InGaAs ； responsivity ； quantum efficiency ； photosensitivity ； GZO ； atomic layer deposition ； RF-sputter ； NiOx ； Schottky barrier height ； Ohmic contact ； transparent-conducting AR coating

參考文獻

[36] P. M. Martin, “Handbook of Deposition Technologies for Films and Coatings 3rd Edition,” Elsevier, Massachusetts, pp. 364-391, 2010.

[23] J. Huang, Z. Ye, H. Chen, B. Zhao, and L. Wang, “Growth of N-doped p-type ZnO films using ammonia as dopant source gas,” J. Mater. Sci. Lett., vol. 22, no. 4, pp. 249-251, 2003.

[7] D. M. Scott, “A 2-color near-infrared sensor for sorting recycled plastic waste,” Meas. Sci. Technol., vol. 6, no. 2, 1995.

[8] Y. H. Huang, C. C. Yang, T. C. Peng, F. Y. Cheng, M. C. Wu, Y. T. Tsai, C. L. Ho, I. M. Liu, C. C. Hong, and C. C. Lin, “10-Gb/s InGaAs p-i-n photodiodes with wide spectral range and enhanced visible spectral response,” IEEE Photon. Technol. Lett., vol. 19, no. 5, pp. 339-341, 2007.

[10] P. Maigne, J. A. Beraldin, T. M. Vanderwel, M. Buchanan, and D. Landheer, “An InGaAs-InP position-sensing photodetector,” IEEE J. Quantum Electron., vol. 26, no. 5, pp. 820-823, 1990.