Design and Analysis of Metal-Oxide-Semiconductor–Capacitor Microring Optical Modulator With Solid-Phase-Crystallization Poly-Silicon Gate

We present a rigorous electrical and optical analysis for a metal-oxide-semiconductor (MOS)-capacitor microring optical modulator on silicon-on-insulator (SOI) with a low-mobility and high optical loss polysilicon gate that could be fabricated by the complementary metal-oxide-semiconductor (CMOS)-compatible solid-phase-crystallization (SPC) process. Critical coupling was designed for the 25.5 mum radius rib-waveguide microring. Modulation speed, operating power at 3.3 V operating voltage, and insertion loss (IL) were analyzed with respect to the doping level of the SPC p-polysilicon gate and the n-crystalline silicon channel. 4.6 times10-2 pJ/mum2 operating power per switch can be achieved with 74 GHz modulation speed for 3 times 1018 cm-3 doping level in both the SPC p-polysilicon gate and the n-crystalline silicon channel. For 40 GHz operation, 10-12 dB IL is achievable with the SPC polysilicon, and 9 dB IL is achievable with the well-annealed polysilicon that is lossless. Tolerance of the critical coupling to the gap width variation, temperature drifting of the microring, and wavelength drifting of the light source were analyzed and discussed extensively, and the extinction ratio (ER) was estimated for various situations. The 90 nm CMOS fabrication specification, if applied to the gap width variation of the microring, would leave a large margin in the ER to other sources of the critical coupling deviation. We found that ~ plusmn0.2degC temperature stability for the microring and the light source is required for a minimum ER of 5 dB if temperatures of both elements are controlled independently. Comparison between the MOS-capacitor modulators with microring and with Mach-Zehnder types was analyzed and discussed. In contrast to the Mach-Zehnder modulator, the modulation speed of the microring can be pushed up by increasing the doping level up to ~ 1times1018 cm-3 without significantly increasing the IL.

[1]  Qianfan Xu,et al.  Micrometre-scale silicon electro-optic modulator , 2005, Nature.

[2]  M. Paniccia,et al.  A high-speed silicon optical modulator based on a metal–oxide–semiconductor capacitor , 2004, Nature.

[3]  R. Shenoy,et al.  Design of a silicon-based field-effect electro-optic modulator with enhanced light-charge interaction. , 2005, Optics letters.

[4]  Coupled mode theory , 2006 .

[5]  Brian Culshaw,et al.  Thermo-optic phase modulators in SIMOX material , 2000, Photonics West - Optoelectronic Materials and Devices.

[6]  Low loss polysilicon waveguides for silicon photonics , 1997 .

[7]  L. Liao,et al.  Optical transmission losses in polycrystalline silicon strip waveguides: Effects of waveguide dimensions, thermal treatment, hydrogen passivation, and wavelength , 2000 .

[8]  B. Riccò,et al.  Quantum-mechanical modeling of accumulation layers in MOS structure , 1992 .

[9]  Simplified numerical method for analyzing TE-like modes in a three-dimensional circularly bent dielectric rib waveguide by solving two one-dimensional eigenvalue equations , 2008 .

[10]  裕幸 飯田,et al.  International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について － , 2004 .

[11]  K. Saraswat,et al.  Low-temperature (, 1992, IEEE Electron Device Letters.

[12]  Desmond Rodney Lim,et al.  Device integration for silicon microphotonic platforms , 2000 .

[13]  Lionel C. Kimerling,et al.  Losses in polycrystalline silicon waveguides , 1996 .

[14]  R. Soref,et al.  All-silicon active and passive guided-wave components for λ = 1.3 and 1.6 µm , 1986 .

[15]  Amal K. Ghosh,et al.  Theory of the electrical and photovoltaic properties of polycrystalline silicon , 1980 .

[16]  K. Okamoto.  Planar Optical Waveguides , 2022, Fundamentals of Optical Waveguides.

[17]  M. Morse,et al.  High speed silicon Mach-Zehnder modulator. , 2005, Optics express.

[18]  Hermann A. Haus,et al.  Coupled-mode theory of optical waveguides , 1987 .

[19]  R. Soref,et al.  Electrooptical effects in silicon , 1987 .

[20]  Fabrication of high-mobility p-channel poly-Si thin film transistors by self-aligned metal-induced lateral crystallization , 1996 .

[21]  H J Shaw,et al.  All-single-mode fiber resonator. , 1982, Optics letters.

[22]  Masaru Takabatake,et al.  CMOS circuits for peripheral circuit integrated poly-Si TFT LCD fabricated at low temperature below 600 degrees C , 1991 .