High-speed Si resonant cavity enhanced photodetectors and arrays

Abstract

Over the past decade a new family of optoelectronic devices has emerged whose performance is enhanced by placing the active device structure inside a Fabry-Perot resonant microcavity ͓P. E. Green, IEEE Spectrum 13 ͑2002͔͒. The increased optical field allows photodetectors to be made thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. We have demonstrated a variety of resonant cavity enhanced ͑RCE͒ photodetectors in compound semiconductors ͓B. Yang, J. D. Schaub, S. M. Csutak, D. J. Rogers, and J. C. Campbell, IEEE Photonics Technol. Lett. 15, 745 ͑2003͔͒ and Si ͓M. K. Emsley, O. I. Dosunmu, and M. S. Ü nlü, IEEE J. Selected Topics Quantum Electron. 8, 948 ͑2002͔͒, operating at optical communication wavelengths ranging from 850 nm to 1550 nm. The focus of this article is on Si photodetectors and arrays. High bandwidth short distance communications standards are being developed based on parallel optical interconnect fiber arrays to meet the needs of increasing data rates of interchip communication in modern computer architecture. To ensure that this standard becomes an attractive option for computer systems, low cost components must be implemented on both the transmitting and receiving end of the fibers. To meet this low cost requirement silicon based receiver circuits are the most viable option, however, high speed, high efficiency silicon photodetectors present a technical challenge. Commercially reproducible silicon wafers with a high reflectance buried distributed Bragg reflector ͑DBR͒ have been designed and fabricated ͓M. K. Emsley, O. I. Dosunmu, and M. S. Ü nlü, IEEE J. Selected Topics Quantum Electron. 8, 948 ͑2002͔͒. The substrates consist of a two-period, 90% reflecting, DBR fabricated using a double silicon-on-insulator ͑SOI͒ process. Resonant-cavity-enhanced ͑RCE͒ Si photodetectors have been fabricated with 40% quantum efficiency at 850 nm and a FWHM of 29 ps suitable for 10 Gbps data communications. Recently, 1ϫ12 photodetector arrays have been fabricated, packaged, and tested with silicon based amplifiers to demonstrate the feasibility of a low cost solution for optical interconnects.

Cavity-Enhanced Near-Infrared Organic Photodetectors Based on a Conjugated Polymer Containing [1,2,5]Selenadiazolo[3,4-c]Pyridine

“…An approach to achieve a spectral response tunable over a broad wavelength range is to incorporate organic semiconductors into a Fabry–Perot cavity device architecture. − To obtain high spectral selectivity, the optical depth (absorption coefficient times thickness) of the photon-active layer sandwiched in between the two mirrors needs to be small. However, the typically very high absorption coefficients of the organic semiconductor, considered for organic photovoltaics or photodetectors, are extremely high to allow narrowband enhancement when incorporated as a 100 nm thin film in a cavity device architecture.…”

Design and Integration of All-Silicon Fiber-Optic Receivers for Multi-Gigabit Chip-to-Chip Links

“…The design and fabrication of arrays of SOI-based resonant-cavity enhanced (RCE) photodetectors with high quantum efficiency, capable of operating at data rates up to 10-Gbps has been previously demonstrated by the authors [2]. The low absorption coefficient of silicon (Si) at 850nm is enhanced by the use of a Fabry-Perot resonator, delimited by the Si-air interface and the 90% reflectivity, two-period Si-Si0 2 distributed Bragg reflector.…”

Organic Cavity Photodetectors Based on Nanometer-Thick Active Layers for Tunable Monochromatic Spectral Response

“…An elegant solution to realize a filterless and narrowband photodetector is to place the photoactive material inside a resonant optical microcavity. This has been demonstrated for both organic − and inorganic materials. − For the latter, near-infrared spectral responses with a full-width-at-half-maximum (fwhm) less than 10 nm have been achieved using two multilayer dielectric mirrors, deposited using epitaxy techniques. , However, the detection range, which is proportional to the distance between the mirrors of the cavity, was limited to a narrow wavelength range of less than 100 nm, due to the rather small free spectral range (FSR, i.e., the wavelength spacing between adjacent resonance peaks). The FSR of a cavity decreases quadratically with decreasing resonance wavelength, and in general, Fabry–Perot cavities yield a polychromatic, overtone containing a response spectrum.…”