論文提要
本論文探討的主題是具非晶矽/非晶碳化矽或非晶矽/非晶矽化鍺薄膜複層之矽基金屬-半導體-金屬光檢測器的特性。在非晶矽/非晶碳化矽複層方面，利用非晶碳化矽與非晶矽的光能隙高度不同所形成的能帶不連續可有效降低元件的暗電流，進而提昇元件在低入射光功率時的光電流與暗電流比值。此種結構元件在非常弱的入射光功率(0.5μW)下，仍可產生相當高的光電流對暗電流比值。此光電流與暗電流比值相較於以往僅具有一層非晶矽薄膜的元件高出近一千倍，如此高靈敏度的光檢測器元件可大幅降低光檢測器在低入射光功率操作時的位元錯誤率(bit error rate)。再者，在一週期性0.83μm 60 ps的光脈衝量測下，此元件暫態響應的平均半高寬(FWHM)和下降時間(fall-time)分別為68.18和294.7 ps。相較於以往的許多矽基光檢測器的報告，本研究探討的元件所採用類量子井的非晶質薄膜複層結構可有效提昇金屬-半導體-金屬矽基光檢測器的靈敏度。另外，具非晶矽/非晶矽化鍺薄膜複層之矽基金屬-半導體-金屬光檢測器的特性亦被加以探討。我們詳盡地探討不同非晶矽/非晶矽化鍺薄膜複層厚度與結構，以及氫氣電漿處理(H2-plasma treatment)非晶質矽化鍺薄膜表面等等實驗因子的改變對元件特性的影響。

Abstract
The planar Si-based metal-semiconductor-metal photodetectors (MSM-PDs) with a-Si:H/a-SiC:H (or a-Si:H/a-SiGe:H) multi-layers to reduce device dark current had been studied. For the ones with a-Si:H/a-SiC:H multi-layers, their sensitivity could be enhanced very effectively. Under a very weak incident light power (0.5 μW) and with a 4 V bias-voltage, the device photo- to dark- current ratio (Ip/Id) could be 103 times higher than that of the previously reported one. Also, the average full-width-at-half-maximum (FWHM) and fall-time of the device temporal response were 68.18 and 294.7 ps, respectively, as measured with a periodic 0.83μm 60 ps light pulse and a 10 V bias-voltage. Comparing to the previously reported various Si-based PDs, this device exhibited significant improvements in device sensitivity and temporal-response due to the employed quantum-well-like amorphous silicon-alloy barrier layers. Moreover, the Si-based MSM-PDs with a-Si:H/a-SiGe:H multi-layers also had been investigated. The effects of multi-layer thickness and structure, and H2-plasma treatment of a-SiGe:H films on device performances had been studied also.

References
[1]D. Knipp, P.G. Herzog, and H. Stiebig, “Stacked amorphous silicon color sensors,” IEEE Trans. Electron Devices, vol. 49,pp. 170-176, 2002.
[2]A.D. Stiff, S. Krishna, P. Bhattacharya, and S. W. Kennerly, “A PMOS tunneling photodetector,” IEEE Trans. Electron Devices, vol. 48,pp. 1747-1749, 2001.
[3]L. H. Laih, T. C. Chang, Y. A. Chen, W. C. Tsay, and J. W. Hong, “A U-Grooved Metal-Semiconductor-Metal Photodetector (UMSM-PD) with an i-a-Si:H Overlayer on a [100] p-Type Si Wafer,” IEEE Photo. Technol. Lett., vol. 10, no. 4, pp. 579-581, 1998.
[4]L. H. Laih, T. C. Chang, Y. A. Chen, W. C. Tsay, and J. W. Hong, “Characteristics of MSM photodetector with trench electrodes on p-type Si wafer,” IEEE Trans. Electron Devices, vol. 45, pp. 2018-2023, 1998.
[5]L. H. Laih, T. C. Chang, Y. A. Chen, W. C. Tsay, and J. W. Hong, “Characteristics of Si-based MSM photodetectors with an amorphous-crystalline heterojunction,” Solid-State Electronics, vol. 41, pp. 1693-1697, 1997.
[6]C. S. Lin, R. H. Yeh, C. H. Liao, and J. W. Hong, “Improving characteristics of Si-based trench-electrode metal-semiconductor- metal photodetectors using self-aligned process,” IEE Proc. Optoelectronics, vol. 148, pp. 195-198, 2001.
[7]S. M. Sze, Physics of Semiconductor Devices, John Wiley & Sons, Inc., 2nd ed, Chap 10, p. 613, 1985.
[8]S. Y. Wang, D. M. Bloom, and D. M. Collins, “Ultrahigh speed photodetectors,” SPIE, vol. 439, pp. 178, 1993.
[9]A. Selvarajan, K. Shenai, Vijai K. Traipathi, Optoelectronics: Technologies and Applications, spie optical engineering press, Chap. 10, pp. 211-218, 1993.
[10]H. Mimura, and Y. Hatanaka, “ Carrier transport mechanisms of p-type amorphous―n-type crystalline silicon heterojunctions,” J. Appl. Phys. vol. 71, pp.2315-2320, 1992.
[11]L. F. Marsal, J. Pallares, and X. Corregi, “Electrical characterization of n-amorphous/p-crystalline silicon heterojunctions,” J. Appl. Phys. vol. 79, pp.8493-8497, 1996.
[12]C. S. Lin, R. H. Yeh, C. H. Liao, and J. W. Hong, “High-speed Si-based metal-semiconductor-metal photodetectors with an additional composition-graded i-a-Si1-xGex:H layer,” Solid-State Electronics, vol. 46, pp. 2027-2033, 2002.