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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. [ABSTRACT FROM AUTHOR]

We report on the noise characterization of photoconductors based on PbS colloidal quantum dots. The devices operate in the near infrared region with peak responsivity exceeding 70 A/W at 1.3 μm at low optical intensity and low voltage bias. The large responsivity, combined with the low dark current of high resistance devices, provides a specific detectivity D* as large as 1011 cm Hz½W-1. The noise characteristics are investigated using noise current spectra measured at different biases both in dark and under optical excitation. The analysis revealed that the noise is clearly dominated by the flicker component up to 100 kHz. The noise performance is investigated at different optical intensities and for different device dimensions and voltage biases. [ABSTRACT FROM AUTHOR]

Germanium is considered the most suitable semiconductor for monolithic integration of near-infrared detectors on silicon photonic chips. Here we report on Ge-on-Si near-infrared photodetectors fabricated by thermal evaporation, demonstrating the use of phosphorus spin-on-dopant to compensate the acceptor states introduced by dislocations. The detectors exhibit 1.55 μm responsivities as high as 0.1 A/W, more than two orders of magnitude larger than in undoped devices and comparing well with state-of-the-art p-i-n photodiodes. This approach enables simple and low-cost monolithic integration of near-infrared sensors with silicon photonics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The authors demonstrate near infrared photodetectors in evaporated germanium on silicon-on-insulator waveguides. The authors achieve peak responsivities as high as 1 A/W and dark current densities as low as 40 nA at a reverse bias of 1 V. Owing to the low deposition temperature, this technology allows for simple and low cost monolithic integration with silicon. [ABSTRACT FROM AUTHOR]

Demonstrates a voltage tunable silicon germanide (SiGe)/Si superlattice photodetector. Capability of SiGe/Si photodetector to do complex mixing functions between optical signals; Calculation of current flow in SiGe/Si device; Development of methods for optical signal encryption based on photodetector characteristics.

We have fabricated Ge/Si heterojunction photodetectors with high responsivities of 550 mA/W at 1.32 μm and 250 mA/W at 1.55 μm and time responses shorter than 850 ps. High quality Ge was epitaxially grown on Si using ultrahigh vacuum/chemical vapor deposition followed by cyclic thermal annealing. The beneficial effect of the post-growth thermal annealing on the electrical properties of Ge epilayers, due to the reduction of threading-dislocation densities, is confirmed by the dramatic enhancement of the performance of the photodetectors. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this letter we report on a metal–semiconductor–metal photodetector based on thick relaxed Ge layers, epitaxially grown on silicon after insertion of a low-temperature-grown Ge buffer layer. The detector shows a good responsivity at normal incidence at both 1.3 and 1.55 μm, with a maximum responsivity of 0.24 A/W at 1.3 μm under a 1 V bias. A response time of about 2 ns has been measured. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]