The design, the realization, and the characterization of silicon resonant cavity enhanced (RCE) photodetectors, working at 1.55？μm, are reported. The photodetectors are constituted by a Fabry-Perot microcavity incorporating a Schottky diode. The working principle is based on the internal photoemission effect. We investigated two types of structures: top and back-illuminated. Concerning the top-illuminated photodetectors, a theoretical and numerical analysis has been provided and the device quantum efficiency has been calculated. Moreover, a comparison among three different photodetectors, having as Schottky metal: gold, silver, or copper, was proposed. Concerning the back-illuminated devices, two kinds of Cu/p-Si RCE photodetectors, having various bottom-mirror reflectivities, were realized and characterized. Device performances in terms of responsivity, free spectral range, and finesse were theoretically and experimentally calculated in order to prove an enhancement in efficiency due to the cavity effect. The back-illuminated device fabrication process is completely compatible with the standard silicon technology. 1. Introduction In the last two decades, there has been growing interest in photonic devices based on Si-compatible materials [1, 2] in the field of both optical telecommunications and optical interconnects. In this context, tremendous progresses in the technological processes have allowed to realize effectively fully CMOS compatible optical components, such as low-loss waveguides, high-Q resonators, high speed modulators, couplers, and optically pumped lasers [3–8]. All these devices have been developed to operate in the wavelength range from the C optical band (1528–1561？nm) to the L optical band (1561–1620？nm) where the defect-free intrinsic bulk Si has minimal absorption. On the other hands, this transparency window limits the Si applications as absorbing material for infrared photodetection, so that the development of high-performance waveguide-integrated photodetectors on Si-CMOS platform has remained an imperative but unaccomplished task. In order to develop all Si photodetectors and to take advantage of the low-cost standard Si-CMOS processing technology without additional materials or process steps, a number of options have been proposed, in particular, the two-photon absorption (TPA) [9], the incorporation of optical dopants/defects with mid-bandgap energy levels into the Si lattice [10, 11], and the internal photoemission effect (IPE) [12]. The IPE has been recently used also in silicon photodetectors realized with plasmonics
References
[1]
L. C. Kimerling, L. Dal Negro, S. Saini, et al., “Monolithic silicon microphotonics,” in Silicon Photonics, L. Pavesi and D. J. Lockwood, Eds., vol. 94 of Topics in Applied Physics, pp. 89–119, Springer, Berlin, Germany, 2004.
[2]
B. Jalali and S. Fathpour, “Silicon photonics,” Journal of Lightwave Technology, vol. 24, no. 12, pp. 4600–4615, 2006.
[3]
L. K. Rowe, M. Elsey, N. G. Tarr, A. P. Knights, and E. Post, “CMOS-compatible optical rib waveguides defined by local oxidation of silicon,” Electronics Letters, vol. 43, no. 7, pp. 392–393, 2007.
[4]
L. Vivien, D. Pascal, S. Lardenois et al., “Light injection in SOI microwaveguides using high-efficiency grating couplers,” Journal of Lightwave Technology, vol. 24, no. 10, pp. 3810–3815, 2006.
[5]
Q. Xu, S. Manipatruni, B. Schmidt, J. Shakya, and M. Lipson, “12.5 Gbit/s carrier-injection-based silicon micro-ring silicon modulators,” Optics Express, vol. 15, no. 2, pp. 430–436, 2007.
[6]
C. P. Michael, M. Borselli, T. J. Johnson, C. Chrystal, and O. Painter, “An optical fiber-taper probe for wafer-scale microphotonic device characterization,” Optics Express, vol. 15, no. 8, pp. 4745–4752, 2007.
[7]
A. Liu, L. Liao, D. Rubin et al., “High-speed optical modulation based on carrier depletion in a silicon waveguide,” Optics Express, vol. 15, no. 2, pp. 660–668, 2007.
[8]
A. Liu, H. Rong, R. Jones, O. Cohen, D. Hak, and M. Paniccia, “Optical amplification and lasing by stimulated Raman scattering in silicon waveguides,” Journal of Lightwave Technology, vol. 24, no. 3, pp. 1440–1455, 2006.
[9]
T. K. Liang, H. K. Tsang, I. E. Day, J. Drake, A. P. Knights, and M. Asghari, “Silicon waveguide two-photon absorption detector at 1.5 μm wavelength for autocorrelation measurements,” Applied Physics Letters, vol. 81, no. 7, p. 1323, 2002.
[10]
J. D. B. Bradley, P. E. Jessop, and A. P. Knights, “Silicon waveguide-integrated optical power monitor with enhanced sensitivity at 1550 nm,” Applied Physics Letters, vol. 86, no. 24, Article ID 241103, 3 pages, 2005.
[11]
H. Chen, X. Luo, and A. W. Poon, “Cavity-enhanced photocurrent generation by 1.55 μm wavelengths linear absorption in a p-i-n diode embedded silicon microring resonator,” Applied Physics Letters, vol. 95, no. 17, Article ID 171111, 2009.
[12]
S. Zhu, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Near-infrared waveguide-based nickel silicide Schottky-barrier photodetector for optical communications,” Applied Physics Letters, vol. 92, no. 8, Article ID 081103, 2008.
[13]
A. Akbari and P. Berini, “Schottky contact surface-plasmon detector integrated with an asymmetric metal stripe waveguide,” Applied Physics Letters, vol. 95, no. 2, Article ID 021104, 2009.
[14]
Y. Wang, X. Su, Y. Zhu et al., “Photocurrent in Ag-Si photodiodes modulated by plasmonic nanopatterns,” Applied Physics Letters, vol. 95, no. 24, Article ID 241106, 2009.
[15]
W. F. Kosonocky, F. V. Shallcross, T. S. Villani, and J. V. Groppe, “ element PtSi Schottky-barrier IR-CCD image sensor,” IEEE Transactions on Electron Devices, vol. 32, no. 8, pp. 1564–1573, 1986.
[16]
R. H. Fowler, “The analysis of photoelectric sensitivity curves for clean metals at various temperatures,” Physical Review, vol. 38, no. 1, pp. 45–56, 1931.
[17]
V. E. Vickers, “Model of Schottky barrier hot-electron-mode photodetection,” Applied Optics, vol. 10, no. 9, pp. 2190–2192, 1971.
[18]
S. M. Sze, Physics of Semiconductor Devices, John Wiley & Sons, New York, NY, USA, 1981.
[19]
H. X. Yuan and A. G. U. Perera, “Dark current analysis of Si homojunction interfacial work function internal photoemission far-infrared detectors,” Applied Physics Letters, vol. 66, no. 17, pp. 2262–2264, 1995.
[20]
M. K. Emsley, O. Dosunmu, and M. S. ünlü, “Silicon substrates with buried distributed Bragg reflectors for resonant cavity-enhanced optoelectronics,” IEEE Journal on Selected Topics in Quantum Electronics, vol. 8, no. 4, pp. 948–955, 2002.
[21]
E. Y. Chan and H. C. Card, “Near IR interband transitions and optical parameters of metal-germanium contacts,” Applied Optics, vol. 19, no. 8, pp. 1309–1315, 1980.
[22]
G. G. Shahidi, “SOI technology for the GHz era,” IBM Journal of Research and Development, vol. 46, no. 2-3, pp. 121–131, 2002.
[23]
E. Y. Chan, H. C. Card, and M. C. Teich, “Internal photoemission mechanisms at interfaces between germanium and thin metal films,” IEEE Journal of Quantum Electronics, vol. 16, no. 3, pp. 373–381, 1980.
[24]
P. Yeh, Optical Waves in Layerer Media, John Wiley & Sons, New York, NY, USA, 1988.
[25]
M. A. Muriel and A. Carballar, “Internal field distributions in fiber Bragg gratings,” IEEE Photonics Technology Letters, vol. 9, no. 7, pp. 955–960, 1997.
[26]
K. Kishino, M. S. Unlu, J. Chyi, J. Reed, L. Arsenault, and H. Morkoc, “Resonant cavity-enhanced (RCE) photodetectors,” IEEE Journal of Quantum Electronics, vol. 27, no. 8, pp. 2025–2034, 1991.
[27]
E. D. Palik, Handbook of Optical Constants of Solids, Academic Press, San Diego, Calif, USA, 1985.
[28]
H. C. Card, “Aluminum-silicon Schottky barriers and ohmic contacts in integrated circuits,” IEEE Transactions on Electron Devices, vol. 23, no. 6, pp. 538–544, 1976.
[29]
K. Vedam, “Spectroscopic ellipsometry: a historical overview,” Thin Solid Films, vol. 313-314, pp. 1–9, 1998.
[30]
G. E. Jellison Jr., “The calculation of thin film parameters from spectroscopic ellipsometry data,” Thin Solid Films, vol. 290-291, pp. 40–45, 1996.
[31]
G. E. Jellison Jr. and F. A. Modine, “Parameterization of the optical functions of amorphous materials in the interband region,” Applied Physics Letters, vol. 69, no. 3, pp. 371–373, 1996.
[32]
G. E. Jellison Jr., F. A. Modine, P. Doshi, and A. Rohatgi, “Spectroscopic ellipsometry characterization of thin-film silicon nitride,” Thin Solid Films, vol. 313-314, pp. 193–197, 1998.
[33]
P. Doshi, G. E. Jellison Jr., and A. Rohatgi, “Characterization and optimization of absorbing plasma-enhanced chemical vapor deposited antireflection coatings for silicon photovoltaics,” Applied Optics, vol. 36, no. 30, pp. 7826–7837, 1997.
[34]
D. E. Aspnes, J. B. Theeten, and F. Hottier, “Investigation of effective-medium models of microscopic surface roughness by spectroscopic ellipsometry,” Physical Review B, vol. 20, no. 8, pp. 3292–3302, 1979.
[35]
S. Donati, Photodetectors: Devices, Circuits, and Applications, Prentice Hall PTR, Upper Saddle River, NJ, USA, 1999.
