近年來,矽鍺整合技術應用於電子元件或是光學元件上漸漸受到矚目，舉例來說，利用鍺材料載子遷移率高的特色做HBT，或是鍺紅外光偵測器。但由於兩個材料的晶格常數有4%的差異，使得矽鍺整合有一定的難度。
該論文是研究遠紅外線波段(1310nm-1550nm)，以鍺為吸收材料的金-半-金對接耦合（Butt-coupling）波導光偵測器製作於矽光子晶片， 目的在於提高光偵測器的光響應（Photoresponse）及操作速度（3dB Bandwidth）。回顧文獻，一般製作對接耦合接面是使用選擇性磊晶法（Selective epitaxial growth），但此法需要較特殊的製程處理，且需要高溫長時間的退火，才能達到高品質單晶鍺且形成對接的耦合介面。
我們提出一個新穎的方法，結合快速熱熔磊晶（Rapid-melt-growth）與自對準微接合技術（Self-align mocrobonding technique）將鍺整合在SOI基板上，成功的製作出奈米間距的矽鍺對接耦合接面，所形成的光偵測器在光響應度上有相當大的提升，且操作速度可達13GHz。而其最大的優勢為成本低、製程簡易、與COMS製程可相容，在未來光連結的應用上將有很大助益。

Monolithic integration of silicon and germanium devices is essential in state-of-the-art electronic and optoelectronic applications; for example, high speed photodetectors, high speed heterojunction bipolar transistors and so on, have been reported with superior performances. However, direct epitaxial growth of Ge on Si is critical due to the 4% lattice mismatch between Ge and Si. Moreover, to reduce the threading dislocation defects at the growth interface, high-temperature annealing or processing is required, challenging the integratibility with electronic devices. Furthermore, for some applications, the Ge structure should be integrated with Si devices on the same plane, which cause the process even critical. In this thesis, we develop a novel process using self-aligned microbonding technique in combination with rapid melt growth method, successfully demonstrating a Ge metal-semiconductor-metal photodetector butt-coupled to a Si waveguide. Compared with evanescently coupled Ge photodetectors, butt-coupling devices have been presented with large photo-responsivity and operation bandwidth. However, they are very difficult to be implemented by the conventional epitaxy process. Here, we design and fabricate this device by using our approach in a much simple way. The measured dark current is small about 0.29μA at 1310nm at -1V bias. The absorption efficiency is very high and the operation speed can be up to 25 GHz, if a contact barrier modulation technique is applied. This device potentially can be integrated with electronic devices and other photonic components, for an application of high-speed optical interconnects.

中文摘要 ………………………………………………………………………………………………………………………… i
Abstract …………………………………………………………………………………………………………………… ii
Acknowledgment …………………………………………………………………………………………………… iii
Table of Contents …………………………………………………………………………………………… iv
List of Figures ………………………………………………………………………………………………… vi
List of Tables …………………………………………………………………………………………………… ix
CHAPTER 1: Introduction ………………………………………………………………………… 1
1.1 Motivation and Background …………………………………………………… 1
1.2 Dissertation Organization …………………………………………………… 2
References ………………………………………………………………………………………………………………… 4
CHAPTER 2: Principles of Ge/Si Photodetectors ……………… 5
2.1 Integrated Ge on Si …………………………………………………………………… 7
2.1.1 Rapid-Melt-Growth Method (RMG) ……………………………………… 7
2.1.2 Beam Release and Ge Self-aligned Microbonded on Si (SAMB) …………………………………………………………………………………………………………………………… 8
2.2 Metal-Semiconductor-Metal Photodetectors …………… 9
2.2.1 Specific coefficients ……………………………………………………………… 10
2.2.2 Structures of Butt-Coupling Ge MSM Photodetectors………………………………………………………………………………………………………… 12
2.2.3 Optical Simulation………………………………………………………………………… 13
2.3 Contact barrier modulation ……………………………………………… 18
References ………………………………………………………………………………………………………………… 20

CHAPTER 3: Fabrication……………………………………………………………………………… 21
3.1 Process Flow and Particulars of Fabricated Process ……………………………………………………………………………………………………………………………………………… 21
3.1.1 Define The Rib SOI Waveguide …………………………………………… 21
3.1.2 The Formation of High quality Ge By Rapid-Melt-Growth (RMG) Method ………………………………………………………………………………………… 23
3.1.3 Self-aligned Microbonding Technique for Making Butt-Coupled Photodetectors ………………………………………………………………………………… 25
3.1.4 Surface Passivation and Metalization ……………………… 26
3.2 Run Card and Recipes ………………………………………………………………… 29
References ………………………………………………………………………………………………………………… 34
CHAPTER 4: Experimental Results …………………………………………………… 35
4.1 Quality of RMG Ge ………………………………………………………………………… 35
4.2 Observation of the Butt-Coupling Interface ……………………………………………………………………………………………………………………………………………… 40
4.3 Dark and Photo Current Measurement …………………………… 41
4.4 High Speed and Eye Diagram Measurement ………………… 47
4.5 Schottky barrier height modulation technique for enhancing speed of photodetctors………………………………………………………… 50
References ………………………………………………………………………………………………………………… 55
CHAPTER 5: Conclusion ……………………………………………………………………………… 56

Chapter1
1. Morse, M., et al., Performance of Ge-on-Si p-i-n photodetectors for standard receiver modules. Ieee Photonics Technology Letters, 2006. 18(21-24): p. 2442-2444.
2. Edwards, E.H., et al., Ge/SiGe asymmetric Fabry-Perot quantum well electroabsorption modulators. Optics Express, 2012. 20(28): p. 29164-29173.
3. Tani, K., et al., Light Detection and Emission in Germanium-on-Insulator Diodes. Japanese Journal of Applied Physics, 2012. 51(4): p. 4.
4. Liu, Y.C., M.D. Deal, and J.D. Plummer, High-quality single-crystal Ge on insulator by liquid-phase epitaxy on Si substrates. Applied Physics Letters, 2004. 84(14): p. 2563-2565.
5. Tseng, C.-K., et al., Self-aligned microbonded Ge/Si PIN waveguide photodetectors. Group IV Photonics (post-deadline sesstion), 2012 Aug.29-31.
6. Assefa, S., et al., CMOS-integrated high-speed MSM germanium waveguide photodetector. Optics Express, 2010. 18(5): p. 4986-4999.

Chapter2
1. Edward, D., Handbook of optical constants of solids. Academic Press NY, 1985.
2. DeRose, C.T., et al., Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current. Optics Express, 2011. 19(25): p. 24897-24904.
3. Vivien, L., et al., Zero-bias 40Gbit/s germanium waveguide photodetector on silicon. Optics Express, 2012. 20(2): p. 1096-1101.
4. Yu, D.S., et al., Performance and potential of germanium on insulator field-effect transistors. Journal of Vacuum Science & Technology A, 2006. 24(3): p. 690-693.
5. Sanz-Velasco, A., et al., Room temperature wafer bonding using oxygen plasma treatment in reactive ion etchers with and without inductively coupled plasma. Journal of the Electrochemical Society, 2003. 150(2): p. G155-G162.
6. Liu, Y.C., M.D. Deal, and J.D. Plummer, High-quality single-crystal Ge on insulator by liquid-phase epitaxy on Si substrates. Applied Physics Letters, 2004. 84(14): p. 2563-2565.
7. Tseng, C.-K., et al., Self-aligned microbonded Ge/Si PIN waveguide photodetectors. Group IV Photonics (post-deadline sesstion), 2012 Aug.29-31.
8. Hwang, J.D. and E.H. Zhang, Effects of a a-Si:H layer on reducing the dark current of 1310 nm metal-germanium-metal photodetectors. Thin Solid Films, 2011. 519(11): p. 3819-3821.
9. Kah-Wee, A., L. Guo-Qiang, and K. Dim-Lee, Germanium Photodetector Technologies for Optical Communication Applications. Semiconductor Technologies, Jan Grym (Ed.), 2010, ISBN: 978-953-307-080-3, InTech, DOI: 10.5772/8572. Available from: http://www.intechopen.com/books/semiconductor-technologies/germanium-photodetector-technologies-for-optical-communication-applications.

Chapter3
1. Tseng, C.-K., et al., Self-aligned microbonded Ge/Si PIN waveguide photodetectors. Group IV Photonics (post-deadline sesstion), 2012 Aug.29-31.
2. Nishimura, T., K. Kita, and A. Toriumi, Evidence for strong Fermi-level pinning due to metal-induced gap states at metal/germanium interface. Applied Physics Letters, 2007. 91(12).

Chapter4
1. Dieter, K.S., Semiconductor Material and Device Characterization. p. 42.
2. Cuttriss, D.B., RELATION BETWEEN SURFACE CONCENTRATION AND AVERAGE CONDUCTIVITY IN DIFFUSED LAYERS IN GERMANIUM. Bell System Technical Journal, March 1961. 40(2): p. 509-521.
3. Sze, S.M. and J.C. Irvin, RESISTIVITY MOBILITY AND IMPURITY LEVELS IN GAAS GE AND SI AT 300 DEGREES K. Solid-State Electronics, 1968. 11(6): p. 599-602.
4. Burroughes, J.H., H-MESFET COMPATIBLE GAAS/ALGAAS MSM PHOTODETECTOR. Ieee Photonics Technology Letters, 1991. 3(7): p. 660-662.
5. Harris, N.C., et al., Noise Characterization of a Waveguide-Coupled MSM Photodetector Exceeding Unity Quantum Efficiency. Journal of Lightwave Technology, 2012. 31(1): p. 23-27.
6. Dieter, K.S., SEMICONDUCTOR MATERIAL AND DEVICE CHARACTERIZATON. 2006. THIRD EDTION(A JOHN WILEY & SONS, INC., PUBLICATION): p. 157-163.
7. Assefa, S., et al., CMOS-integrated high-speed MSM germanium waveguide photodetector. Optics Express, 2010. 18(5): p. 4986-4999.
8. Burm, J. and L.F. Eastman, Low-frequency gain in MSM photodiodes due to charge accumulation and image force lowering. Ieee Photonics Technology Letters, 1996. 8(1): p. 113-115.