Ge/Sige Asymmetric Fabry-Perot Quantum Well Electroabsorption Modulators
Total Page：16
File Type：pdf, Size：1020Kb
Ge/SiGe asymmetric Fabry-Perot quantum well electroabsorption modulators Elizabeth H. Edwards,1,∗ Ross M. Audet,1 Edward T. Fei,1 Stephanie A. Claussen,1 Rebecca K. Schaevitz,2 Emel Tasyurek,1 Yiwen Rong,3 Theodore I. Kamins,1 James S. Harris,1 and David A. B. Miller1 1Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA 2Current address: Corning West Technology Center, Palo Alto, CA 94304, USA 3Current address: Philips LumiLEDs, San Jose, CA 95131, USA ∗[email protected] Abstract: We demonstrate vertical-incidence electroabsorption mod- ulators for free-space optical interconnects. The devices operate via the quantum-confined Stark effect in Ge/SiGe quantum wells grown on silicon substrates by reduced pressure chemical vapor deposition. The strong electroabsorption contrast enables use of a moderate-Q asymmetric Fabry-Perot resonant cavity, formed using a film transfer process, which allows for operation over a wide optical bandwidth without thermal tuning. Extinction ratios of 3.4 dB and 2.5 dB are obtained for 3 V and 1.5 V drive swings, respectively, with insertion loss less than 4.5 dB. For 60 µm diameter devices, large signal modulation is demonstrated at 2 Gbps, and a 3 dB modulation bandwidth of 3.5 GHz is observed. These devices show promise for high-speed, low-energy operation given further miniaturization. © 2012 Optical Society of America OCIS codes: (230.4110) Modulators; (230.4205) Multiple quantum well (MQW) modulators; (200.4650) Optical Interconnects; (250.0250) Optoelectronics. References and links 1. D. A. B. Miller, “Device requirements for optical interconnects to silicon chips,” Proc. IEEE 97, 1166–1185 (2009). 2. G. T. Reed, G. Mashanovich, F. Y. Gardes, and D. J. Thomson, “Silicon optical modulators,” Nat. Photonics 4, 518–526 (2010). 3. J. Liu, M. Beals, A. Pomerene, S. Bernardis, R. Sun, J. Cheng, L. C. Kimerling, and J. Michel, “Waveguide- integrated, ultralow-energy GeSi electro-absorption modulators,” Nat. Photonics 2, 433–437 (2008). 4. D. Feng, S. Liao, H. Liang, J. Fong, B. Bijlani, R. Shafiiha, B. J. Luff, Y. Luo, J. Cunningham, A. V. Krish- namoorthy, and M. Asghari, “High speed GeSi electro-absorption modulator at 1550 nm wavelength on SOI waveguide,” Opt. Express 20, 22224–22232 (2012). 5. Y.-H. Kuo, Y. K. Lee, Y. Ge, S. Ren, J. E. Roth, T. I. Kamins, D. A. B. Miller, and J. S. Harris, “Quantum-confined Stark effect in Ge/SiGe quantum wells on Si for optical modulators,” IEEE J. Sel. Top. Quantum Electron. 12, 1503–1513 (2006). 6. S. Ren, Y. Rong, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “Selective epitaxial growth of Ge/Si0.15Ge0.85 quantum wells on Si substrate using reduced pressure chemical vapor deposition,” Appl. Phys. Lett. 98, 151108 (2011). 7. R. K. Schaevitz, J. E. Roth, S. Ren, O. Fidaner, and D. A. B. Miller, “Material properties of Si-Ge/Ge quantum wells,” IEEE J. Sel. Top. Quantum Electron. 14, 1082–1089 (2008). 8. R. Schaevitz, E. Edwards, J. Roth, E. Fei, Y. Rong, P. Wahl, T. Kamins, J. Harris, and D. Miller, “Simple elec- troabsorption calculator for designing 1310 nm and 1550 nm modulators using germanium quantum wells,” IEEE J. Quantum Electron. 48, 187–197 (2012). #177465 - $15.00 USD Received 1 Nov 2012; revised 7 Dec 2012; accepted 10 Dec 2012; published 17 Dec 2012 (C) 2012 OSA 17 December 2012 / Vol. 20, No. 27 / OPTICS EXPRESS 29164 9. L. Lever, Z. Ikonic, A. Valavanis, J. Cooper, and R. Kelsall, “Design of Ge/SiGe quantum-confined Stark ef- fect electroabsorption heterostructures for CMOS compatible photonics,” J. Lightwave Technol. 28, 3273–3281 (2010). 10. J. E. Roth, O. Fidaner, R. K. Schaevitz, Y. Kuo, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “Optical modulator on silicon employing germanium quantum wells,” Opt. Express 15, 5851–5859 (2007). 11. Y. Rong, Y. Ge, Y. Huo, M. Fiorentino, M. Tan, T. Kamins, T. Ochalski, G. Huyet, and J. Harris, “Quantum- confined Stark effect in Ge/SiGe quantum wells on Si,” IEEE J. Sel. Top. Quantum Electron. 16, 85–92 (2010). 12. E. H. Edwards, R. M. Audet, S. A. Claussen, R. K. Schaevitz, E. Tasyurek, S. Ren., O. I. Dosunmu, M. S. Unl¨ u,¨ and D. A. B. Miller, “Si-Ge surface-normal asymmetric Fabry-Perot quantum-confined Stark effect electroab- sorption modulator,” in “Proc. IEEE Photonics Society Summer Topical Meetings, Playa del Carmen, Mexico,” 211–212 (2010). 13. S. Ren, Y. Rong, S. Claussen, R. Schaevitz, T. Kamins, J. Harris, and D. Miller, “A Ge/SiGe quantum well waveg- uide modulator monolithically integrated with SOI waveguides,” in “2011 8th IEEE International Conference on Group IV Photonics (GFP),” 11–13 (2011). 14. P. Chaisakul, D. Marris-Morini, M.-S. Rouifed, G. Isella, D. Chrastina, J. Frigerio, X. Le Roux, S. Edmond, J.-R. Coudevylle, and L. Vivien, “23 GHz Ge/SiGe multiple quantum well electro-absorption modulator,” Opt. Express 20, 3219–3224 (2012). 15. M. Whitehead and G. Parry, “High-contrast reflection modulation at normal incidence in asymmetric multiple quantum well Fabry-Perot structure,” Electron. Lett. 25, 566–568 (1989). 16. R. H. Yan, R. J. Simes, and L. A. Coldren, “Surface-normal electroabsorption reflection modulators using asym- metric Fabry-Perot structures,” IEEE J. Quantum Electron. 27, 1922–1931 (1991). 17. C. C. Barron, C. J. Mahon, B. J. Thibeault, and L. A. Coldren, “Design, fabrication and characterization of high- speed asymmetric Fabry-Perot modulators for optical interconnect applications,” Opt. Quantum Electron. 25, S885–S898 (1993). 18. F. B. McCormick, T. J. Cloonan, F. A. P. Tooley, A. L. Lentine, J. M. Sasian, J. L. Brubaker, R. L. Morrison, S. L. Walker, R. J. Crisci, R. A. Novotny, S. J. Hinterlong, H. S. Hinton, and E. Kerbis, “Six-stage digital free-space optical switching network using symmetric self-electro-optic-effect devices,” Appl. Opt. 32, 5153–5171 (1993). 19. A. G. Kirk, D. V. Plant, T. H. Szymanski, Z. G. Vranesic, F. A. P. Tooley, D. R. Rolston, M. H. Ayliffe, F. K. Lacroix, B. Robertson, E. Bernier, and D. F.-Brosseau, “Design and implementation of a modulator-based free- space optical backplane for multiprocessor applications,” Appl. Opt. 42, 2465–2481 (2003). 20. M. Haney, M. Christensen, P. Milojkovic, G. Fokken, M. Vickberg, B. Gilbert, J. Rieve, J. Ekman, P. Chandra- mani, and F. Kiamilev, “Description and evaluation of the FAST-Net smart pixel-based optical interconnection prototype,” Proc. IEEE 88, 819–828 (2000). 21. R. M. Audet, E. H. Edwards, P. Wahl, and D. A. B. Miller, “Investigation of limits to the optical performance of asymmetric Fabry-Perot electroabsorption modulators,” IEEE J. Quantum Electron. 48, 198–209 (2012). 22. A. Nayfeh, C. O. Chui, K. C. Saraswat, and T. Yonehara, “Effects of hydrogen annealing on heteroepitaxial-Ge layers on Si: Surface roughness and electrical quality,” Appl. Phys. Lett. 85, 2815–2817 (2004). 23. S. Ren, “Ge/SiGe quantum well waveguide modulator for optical interconnect systems,” Ph.D. thesis, Stanford University (2011). 24. P. Zouganeli, P. J. Stevens, D. Atkinson, and G. Parry, “Design trade-offs and evaluation of the performance attainable by GaAs − Al0.3Ga0.7As asymmetric Fabry-Perot modulators,” IEEE J. Quantum Electron. 31, 927– 943 (1995). 25. P. Zouganeli and G. Parry, “Evaluation of the tolerance of asymmetric Fabry-Perot modulators with respect to realistic operating conditions,” IEEE J. Quantum Electron. 31, 1140–1151 (1995). 26. M. Schmidt, “Wafer-to-wafer bonding for microstructure formation,” Proc. IEEE 86, 1575–1585 (1998). 27. C. L. Mitsas and D. I. Siapkas, “Generalized matrix method for analysis of coherent and incoherent reflectance and transmittance of multilayer structures with rough surfaces, interfaces, and finite substrates,” Appl. Opt. 34, 1678–1683 (1995). 28. L. M. Giovane, H.-C. Luan, A. M. Agarwal, and L. C. Kimerling, “Correlation between leakage current density and threading dislocation density in SiGe p-i-n diodes grown on relaxed graded buffer layers,” Appl. Phys. Lett. 78, 541–543 (2001). 29. E. Onaran, M. C. Onbasli, A. Yesilyurt, H. Y. Yu, A. M. Nayfeh, and A. K. Okyay, “Silicon-germanium multi- quantum well photodetectors in the near infrared,” Opt. Express 20, 7608 (2012). 30. C. Barron, C. Mahon, B. Thibeault, G. Wang, W. Jiang, L. Coldren, and J. Bowers, “Millimeter-wave asymmetric Fabry-Perot modulators,” IEEE J. Quantum Electron. 31, 1484–1493 (1995). 31. D. A. B. Miller, “Energy consumption in optical modulators for interconnects,” Opt. Express 20, A293–A308 (2012). 32. J. J. Lin, A. M. Roy, A. Nainani, Y. Sun, and K. C. Saraswat, “Increase in current density for metal contacts to n-germanium by inserting TiO2 interfacial layer to reduce Schottky barrier height,” Appl. Phys. Lett. 98, 092113 (2011). 33. S. A. Claussen, E. Tasyurek, J. E. Roth, and D. A. B. Miller, “Measurement and modeling of ultrafast carrier dy- namics and transport in germanium/silicon-germanium quantum wells,” Opt. Express 18, 25596–25607 (2010). #177465 - $15.00 USD Received 1 Nov 2012; revised 7 Dec 2012; accepted 10 Dec 2012; published 17 Dec 2012 (C) 2012 OSA 17 December 2012 / Vol. 20, No. 27 / OPTICS EXPRESS 29165 34. R. K. Schaevitz, D. S. Ly-Gagnon, J. E. Roth, E. H. Edwards, and D. A. B. Miller, “Indirect absorption in germanium quantum wells,” AIP Advances 1, 032164 (2011). 35. M. S. Rouifed, P. Chaisakul, D. Marris-Morini, J. Frigerio, G. Isella, D. Chrastina, S. Edmond, X. L. Roux, J.-R. Coudevylle, and L. Vivien, “Quantum-confined Stark effect at 1.3 µminGe/Si0.35Ge0.65 quantum-well structure,” Opt. Lett. 37, 3960–3962 (2012). 36. O. Dosunmu, D. Cannon, M. Emsley, L. Kimerling, and M. Unlu, “High-speed resonant cavity enhanced Ge photodetectors on reflecting Si substrates for 1550-nm operation,” IEEE Photon.