Due to recent breakthroughs, silicon photonics is now the most active discipline within the field of integrated optics and, at the same time, a present reality with commercial products available on the market. Silicon photodiodes are excellent detectors at visible wavelengths, but the development of high-performance photodetectors on silicon CMOS platforms at wavelengths of interest for telecommunications has remained an imperative but unaccomplished task so far. In recent years, however, a number of near-infrared all-silicon photodetectors have been proposed and demonstrated for optical interconnect and power-monitoring applications. In this paper, a review of the state of the art is presented. Devices based on mid-bandgap absorption, surface-state absorption, internal photoemission absorption and two-photon absorption are reported, their working principles elucidated and their performance discussed and compared.

In this letter, a near infrared all-silicon (all-Si) photodetector integrated into a silicon-on-insulator waveguide is demonstrated. The device is based on the internal photoemission effect through a metal/Si Schottky junction placed transversally to the optical field confined into the waveguide. The technological steps utilized to fabricate the device allow an efficiently monolithic integration with complementary metal-oxide semiconductor compatible structures. Preliminary results show a responsivity of 0.08 mA/W at 1550 nm with a reverse bias of 1 V and an efficient behavior both in C and L band. Finally, an estimation of bandwidth for GHz range is deduced.

In this paper, the realization and the characterization of a resonant cavity enhanced (RCE) photodetector, completely silicon compatible and working at 1.55μm, are reported. The detector is a RCE structure incorporating a Schottky diode and its working principle is based on the internal photoemission effect. Taking advantage of a Cu∕Si Schottky diode fed on a high reflectivity Bragg mirror, an improvement in responsivity at 1.55μm is experimentally demonstrated.

Design, fabrication, and characterization of an asymmetric metal-semiconductor-metal photodetector, based on internal photoemission effect and integrated into a silicon-on-insulator waveguide, are reported. For this photodetector, a responsivity of 4.5 mA/W has been measured at 1550 nm, making it suitable for power monitoring applications. Because the absorbing metal is deposited strictly around the vertical output facet of the waveguide, a very small contact area of about 3 µm² is obtained and a transit-time-limited bandwidth of about 1 GHz is demonstrated. Taking advantage of this small area and electrode asymmetry, a significant reduction in the dark current (2.2 nA at −21 V) is achieved. Interestingly, applying reverse voltage, the photodetector is able to tune its cut-off wavelength, extending its range of application into the MID infrared regime.

We have fabricated a microarray of porous silicon Bragg reflectors on a crystalline silicon substrate using a technological process based on standard photolithography and electrochemical anodization of the silicon. The array density is of 170 elements/cm2 and each element has a diameter of 200 μm. The porous silicon structures have been used as platform to immobilize an amino terminated DNA single strand probe. All fabrication steps have been monitored by spectroscopic reflectometry, optical and electron microscopy, and Fourier transform infrared spectroscopy. A label-free detection method has been employed to investigate the hybridization between micromolar DNA probe and its complementary target. Due to fast and low cost production, good reproducibility, and high quality optical features, this platform could be adopted also for other different microarray applications such as proteomics and medical diagnostics.