在本論文中，以薄膜電晶體(thin film transistors，TFTs)的結構，將鍺(Ge)量子點耦合在TFTs結構的上部閘介電層(gate dielectrics)中，讓鍺量子點作為光檢測的媒介，將藍光到近紫外光波段的光信號轉換成電信號，再藉由TFTs將電訊號放大，傳輸到下一級。如此一來，不但能減少信號從光檢測器到放大器的損耗，更進一步，也藉此TFTs形成一種光電晶體(phototransistors，PTs)，兼具光檢測器與放大器的功能。在波長405 nm－450 nm的光源照射下，含有鍺量子點的poly-Si TFTs除了對汲極電流有明顯的的?益之外，比起未照光的情況下，元件的次臨限特性都得到良好的改善。造成元件特性照光後有明顯改善的原因源自於只有光激發所產生的電洞注入通道之中，而與電洞對應所產生的電子並未注入通道參與反應，因此在一層鍺量子點薄膜電晶體的ID-VG曲線中並無發現在照光後有電子累積在源極與通道間導致能障降低所引發次臨限特性衰減的現象。

This thesis demonstrates that polycrystalline silicon (poly-Si) thin-film transistors (TFTs) incorporating germanium (Ge) quantum dots (QDs) in the gate oxide were fabricated as efficient blue to near ultraviolet phototransistors for light detection and amplification. Under 405–450 nm light illumination, Ge QDs poly-Si TFTs exhibit not only strong photoresponses in the drive current but also much improved subthreshold characteristics than that measured in darkness. This originates from the fact that only photoexcited holes within Ge QDs are injected into the active channel via vertical electric field and contribute excess mobile carriers for photocurrent but without the associated photogenerated electron induced junction barrier lowering.

[1] D. A. B. Miller, "Physical reasons for optical interconnection," Int. J. Optoelectron. 11, 155, 1997.
[2] J. A. Davis et al., “Interconnect limits on gigascale integration (GSI) in the 21st century,” Proc. IEEE, 89, 305, 2001.
[3] H. Cho, P. Kapur, and K. C. Saraswat, "Power comparison between high-speed electrical and optical interconnects for interchip communication," IEEE J. Lightwave Technol., 22, 2021, 2004.
[4] J. Bautista, “Terra-scale computing – the role of interconnects in volume compute platforms,” Proc. IEEE Int. Interconnect Technol. Conf., 187, 2007.
[5] M. Berekovic, H. J. Stolberg, and Peter Pirsch, “Multicore system-on-chip architecture for MPEG-4 streaming video,” IEEE Trans. Circuit Syst. Video. Technol., 12, 688, 2002.
[6] M. Haurylau et al., “On-chip optical interconnect roadmap: Challenges and critical directions,” IEEE J. Sel. Top. Quantum Electron., 12, 1699, 2007.
[7] M. Herrscher et al., “Epitaxial liftoff InGaAs/InP MSM photodetectors on Si,” Electron. Lett., 31, 1383, 1995.
[8] R. H.Walden, “A review of recent progress in InP-based optoelectronic integrated circuit receiver front-ends,” Int. J. High Speed Electron. Syst., 9, 631, 1998.
[9] J. E. Roth et al., “Optical modulator on Si employing Ge quantum wells,” Frontiers in Optics., 2007.
[10] D. Ahn et al., “High performance, waveguide integrated Ge photodetectors,” Opt. Exp., 15, 3916, 2007.
56
[11] S. J. Koester et al., “Germanium on SOI infrared detectors for integrated photonic applications,” IEEE J. Sel. Topics Quantum Electron., 12, 1489, 2006.
[12] H. Cho, P. Kapur, and K. C. Saraswat, “The impact of technology on power for highspeed electrical and optical interconnects,” Proc. IEEE IITC, 177, 2005.
[13] J. N. Shive, “A new germanium photo-resistance cell,” Phs. Rev., 76, 575, 1949.
[14] W. Shockley, M. Sparks, and G. K. Teal, “P-n junction transistors,” Phs. Rev., 83, 151, 1951.
[15] J. N. Shive, “The properties of germanium phototransistors,” J. Opt. Soc. Am., 43, 239, 1953.
[16] S. M. Ryvkin, “Photoelectric effects in semiconductors,” Consultants Bureau, p. 376, 1964.
[17] L. E. Tsyrlin, “Response of a phototransistor,” Sov. Phys. Semicond., 11, 1127, 1977.
[18] H. Kroemer, “Quasi-electric and quasi-magnetic fields in nonuniform semiconductors,” RCA Rev., 18, 332, 1957.
[19] H. Kroemer, “Theory of wide-gap emitter for transistors,” Proc. IRE, 45, 1535, 1957.
[20] C. W. Chen, and T. K. Gustafson, “Characteristics of an avalanche phototransistor fabricated on a Si surface,” Appl. Phys. Lett., 39, 161, 1981.
[21] J. C. Campbell et al., “Avalanche InP/InGaAs heterojunction phototransistor,” IEEE J. Quantum Electron., 19, 1134, 1983.
57
[22] W. T. Lai and P. W. Li, ” Growth kinetics and related physical/electrical properties of Ge quantum dots formed by thermal oxidation of Si1−xGex-on-insulator,” Nanotechnology, 18 145402, 2007.
[23] P. W. Li et al., “Optical and Electronic Characteristics of Germanium Quantum Dots Formed by Selective Oxidation of SiGe/Si-on-Insulator,” Jpn. J. Appl. Phys., 43, 7788, 2004.
[24] S. S. Tseng and P. W. Li, “Enhanced 400-600 nm photoresponsivity of metal-oxide-semiconductor diodes with multi-stack germanium dots,” Nanotechnology, 19, 235203, 2008.
[25] Yong-Young Noh et al., “Effect of light irradiation on the characteristics of organic field-effect transistors,” J. Appl. Phys. 100, 094501, 2006
[26] H. K. Liou, P. Mei, U. Gennser, and E. S. Yang, “Effects of Ge concentration on SiGe oxidation behavior,” Appl. Phys. Lett., 59, p1200, 1991.
58