Search

We report on Ge Schottky photodiodes epitaxially grown on Si (100) exhibiting a good responsivity in the near infrared up to 1.55 mu m. The Ge epitaxial layers, grown by ultrahigh vacuum chemical vapor deposition, were deposited in two steps differing by the substrate temperature. With this procedure it was possible to obtain films thicknesses comparable with light penetration depth in the 1.3-1.6 mu m range. The photodiodes have a photocurrent which increases as a function of voltage bias, reaching a maximum responsivity of 0.12 A/W at 1.3 mu m under a reverse bias of 4 V. The leakage current density at the saturation voltage is 1 nA/mu m(2). The results show that the proposed approach is promising for the fabrication of 1.3-1.55 mu m near-infrared photodetectors integrated on silicon chips

Photodetectors based on a Ge-on-Si platform were widely studied over the last two decades, rapidly becoming the technology of choice for CMOS-integrated optoelectronic systems operating in the near infrared. Recently, we demonstrated a proof-of-concept device realized with a back-to-back, Ge-on-Si double photodiode with dual-band optical sensitivity and voltage-tunablity characteristics. Such a device represents the cornerstone for the development of integrated imaging systems operating both in the visible and in the near infrared spectral ranges. To achieve this ambitious goal, however, several technology improvements are needed starting from the fabrication of a multipixel array of dual-band photodetectors. Moreover, given the peculiar electronic behavior of the proposed device, specific readout electronics must be developed and integrated onto a CMOS platform. In this paper we demonstrate the operation of a Ge-on-Si multipixel array with a custom-developed readout integrated chip. We show a complete system characterization, also demonstrating its imaging capabilities with a simple experiment for the determination of the intensity profile of two different laser beams.

Detection of explosive traces in the vapor phase is of primary importance for safety and security in several environments. Different detection methods with high sensitivity are available in the market, but they are typically expensive and require specialized personnel to be operated. Here, we propose a compact, low-cost sensor for explosive detection based on the photoluminescence (PL) quenching of solid-state PbS quantum dot solids cast from the solution phase on a silicon substrate. We demonstrate the sensor capability to detect nitrobenzene vapor at a concentration as low as 445 ppb in air at room temperature, overcoming the performance of other state-of-the-art quantum dot-based PL sensors for nitroaromatic compounds. Moreover, the proposed system can be realized with off-the-shelf electronics and does not need any additional laboratory equipment to be operated, thus paving the way for its deployment in distributed sensor networks.

Extending and controlling the spectral range of light detectors is very appealing for several sensing and imaging applications. Here we report on a normal incidence dual band photodetector operating in the visible and near infrared with a bias tunable spectral response. The device architecture is a germanium on silicon epitaxial structure made of two back-to-back connected photodiodes. The photodetectors show a broad photoresponse extending from 390nm to 1600nm with the capability to electronically select the shorter (400-1100 nm) or the longer (1000-1600 nm) portion with a relatively low applied voltage. Devices exhibit peak VIS and NIR responsivities of 0.33 and 0.63 A/W, respectively, a low optical crosstalk (120dB) and, thanks to their low voltage operation, maximum specific detectivities of 7·1011cmHz1/2/W and 2·1010cmHz1/2/W in the VIS and NIR, respectively.

We report oil novel pn Ge photodetectors fabricated oil glass The fabrication consists of wafer bonding and layer splitting. followed by a low-temperature epitaxial growth of Ge The photodiodes are characterized in terms of dark current and responsivity, and their performance compared with devices realized on either Ge or Si The minimum current density is 50 mu A/cm(2) at 1 V reverse bias. the responsivity is 0.2 A/W in the photovoltaic mode, with a maximum of 0 28 A/W at 1.55 micron at a reverse voltage of 5 V (C) 2009 Elsevier

We review near-infrared detectors in germanium grown on silicon. We discuss pn and pin photodiodes based on Ge deposited on Si by a number of techniques, including thermal evaporation; the optical and electronic characterization of Ge-on-Si heterostructures using various approaches to minimize the density of defects; and compatibility issues with standard fabrication processes for Si electronics. We describe in greater detail the most promising devices realized by us and operating either at normal incidence or in guided-wave geometries, with applications to high-speed optical receivers, as well as image sensors.

We investigate the temperature dependence of p-i-n photodetectors realized in germanium on silicon. The dark current increases by a factor 1.6-1.9 every 10 degrees C and is typically dominated by generation in the space charge region, with diffusion contributing in the best samples. The near infrared (NIR) responsivity decreases with temperature in devices with a large defect-density, but is more stable in high-quality photodiodes. These findings provide a relevant insight on the design of Ge-on-Si NIR detectors to be operated above room temperature. (C) 2008 Elsevier B.V. All rights reserved.

We investigate the temperature dependence of germanium on silicon p-i-n photodetectors in terms of both dark current density and near-infrared responsivity. The dark current increases by nearly a factor 1.6 every 10 degrees C, consistently with carrier generation in the space charge region. The responsivity has a complex trend, its temperature variation depending on wavelength and on the germanium quality. Detectors with a large defect density in the active layer exhibit a reduced responsivity as the temperature increases.

We investigate and characterize p-i-n near-infrared photodiodes fabricated in Ge-on-Si by reduced-pressure chemical vapor deposition, a technology compatible with silicon processing. The detectors exhibit remarkably low dark current densities of 1mA/cm(2) at unity reverse bias and high responsivities of 200 mA/W at 1.55 mu m. We evaluated their small-signal resistance, capacitance, and bandwidth as well as eye-diagrams at 2.5 and 10 Gbit/s.

Using differential optical absorption spectroscopy of germanium thin films epitaxially grown on silicon, we accurately evaluate the near-infrared absorption versus wavelength and temperature. The results allow for optimized design and realization of Ge-on-Si photodetectors. (C) 2008 American Institute of Physics.

The authors demonstrate a two-dimensional array of Si-integrated photodetectors equipped with readout electronics and operating in the near infrared. The chip is realized in polycrystalline Ge on a silicon complementary metal oxide semiconductor circuitry and includes 512 pixels, 64 analog to digital converters, dark current cancellation, and test/calibration facilities. They describe its design, fabrication, characterization, and operation as a near-infrared image sensor.

We demonstrate near-infrared Ge-on-Si photodiodes designed to minimize the dark current density and fabricated by chemical vapor deposition. The p-i-n detectors exhibit record low dark currents of 7 nA at 1-V reverse bias with responsivities close to the theoretical maximum. An excellent performance is ascertained,even for very low reverse voltages.

We report on fast p-i-n photodetectors operating in the near infrared and realized in pure germanium on silicon. The diodes were fabricated by chemical vapor deposition at 600 degrees C without affecting the crystal quality and allowing the integration with standard silicon processes. We demonstrate responsivities of 0.4 and 0.2 A/W at 1.3 and 1.55 mu m, respectively, as well as operation at 10 Gbit/s. (c) 2006 American Institute of Physics.

We demonstrate novel near-infrared waveguide photodetectors in polycrystalline germanium deposited on silicon-on-insulator at low temperatures. We present the design, fabrication, and characterization of two photodiodes and their comparison. Without optimization, at 1.55 /spl mu/m, we measured wall-plug and effective responsivities as high as 30 mA/W and in excess of 150 mA/W, respectively.

We report on fast p-i-n near infrared photodetectors in pure germanium on silicon. The diodes were fabricated by chemical vapor deposition at 600 degrees C followed by thermal annealing at 900 degrees C. We also verified that bypassing the thermal treatment did not have significant effects on the resulting crystal quality, allowing to considerably reducing the thermal budget hence simplify the integration with silicon. We demonstrate the operation of photodiodes with responsivities of 0.4 and 0.2A/W at 1.3 and 1.55 mu m, respectively, as well as open-eye diagrams at 10 Gbit/s. (c) 2006 Elsevier B.V. All rights reserved.

Using a guided wave configuration, we demonstrate a novel polyGe-on-Si heterostructure photodetector realized on a silicon-on-insulator by a low deposition temperature process. Without further detector optimization, at 1.55 mu m we measured wall-plug responsivities as high as 15 mA/W with an effective responsivity in excess of 300 mA/W. Device operation was demonstrated up to 2.5 Gbit/s. (C) 2005 American Institute of Physics.

We describe a linear array of Ge-Si heterojunction photodiodes monolithically integrated on a complementary metal-oxide-semiconductor (CMOS) integrated circuit for detection and imaging in the near infrared. Detectors are realized by thermal evaporation of Ge films at the end of the standard CMOS process on substrates held at low temperature (300/spl deg/C). Each of the 64 detectors is connected to a front-end stage for photocurrent integration and analog-to-digital conversion.

We report on a fast polycrystalline germanium-on-silicon heterojunction photodetector for the near-infrared. The device exhibits a pulse response faster than 200 ps, allowing operation at 2.5 Gbit/s as testified by open eye diagrams. This polycrystalline device, with responsivities of 16 and 5 mA/W at 1.3 and 1.55 mum, respectively, and dark currents of 1 mA/cm(2), is entirely integrable on standard silicon electronics and is an appealing low-cost candidate for fiber-to-the-home communication networks. (C) 2003 American Institute of Physics.

Si based optoelectronic devices have recently successfully entered the market of optical communications, This fact is stimulating renewed efforts in the design of optoelectronic components based on the well-established Si technology. In this paper, the motivations supporting these efforts and the major obstacles to be overcome are presented. Moreover, an overview of the state of the art of different classes of silicon based optoelectronic devices (waveguides, detectors, light sources etc.) is given. (C) 2002 Elsevier Science B.V. All rights reserved.

A novel solid-stale device for the spectral analysis of near infrared light is presented. The device is an array of six photodetectors in polycrystalline Ge on Si, each element being wavelength selective. The fabrication, characterisation and demonstration of the device both as a wavelength meter and spectrum analyser are presented.

Due to the evergrowing use of optical fibers in communications, for both long distances and local area networks, there is an increasing effort toward the realization of high speed and high efficiency optical detectors, operating in the low-absorption regions ~1.3‐1.55 mm! of silica fibers. Although III‐V semiconductors provide high detection efficiency in the range of interest, incorporating them in the well-established Si technology is difficult and expensive. 1 SiGe structures on silicon represent an alternative solution for near-infrared photodetection, owing to their narrow band gap and full compatibility with silicon technologies. SiGe alloy heterostructures, multiquantum wells, and superlattices have been used as active layers in p-i-n photodetectors and their operation at 1.3 mm has been successfully demonstrated for both normal incidence 2 and waveguide configurations. 3 The fundamental limitation of SiGe-based heterostructures is the vanishing response at 1.55 mm. Pure germanium, indeed, represents the best candidate for 1.3‐1.55 mm photodetectors, due to its direct band gap of 0.8 eV. However, owing to the high lattice mismatch with Si, it is not easy to obtain Ge films with suitable characteristics: thickness appropriate for maximum efficiency, flatness compatible with submicron lithography, minimum defect content for high speed. Thick graded buffers can be used to partially relax the strain due to the lattice mismatch, 4 but the molecular beam epitaxy ~MBE! growth of such a layer is cumbersome and expensive. In the present work we investigate the feasibility of the simplest fabrication approach, i.e., the epitaxial growth of thick layers ~well over the critical thickness! of pure germanium on silicon by chemical vapor deposition ~CVD!. The use of pure Ge on Si for efficient photon detection in the range 1.3‐1.5 mm, first attempted by Luryi et al., 5 requires

We report on Ge Schottky diodes epitaxially grown on Si(001) exhibiting a good responsivity in the near-infrared up to 1.55 mu m. The Ge layers were grown by UHV chemical vapor deposition. It was found that the photocurrent increases upon increasing the reverse bias, reaching a maximum responsivity of 0.12 A/W at 1.3 mu m for 4 V bias. The leakage current density at the saturation voltage is 1 nA/mu m(2).

We report on the state of the art of near infrared photodetectors based on germanium on silicon. After a brief review on material and devices, we describe our approach to the fabrication of fast Ge/Si p-i-n detectors based on a simple process with reduced thermal budget for compatibility with standard silicon technology. The diodes, fabricated by chemical vapor deposition at 600°C, exhibit responsivities of 0.4 and 0.2A/W at 1.3μm and 1.55μm, respectively, and operation at 10Gbit/s. copyright The Electrochemical Society.