Calculation of Ge0.5Si0.5-Si Superlattice Photodetectors on Ge0.05Si0.95 Waveguides:The Optimum Parameters^①

The optimum parameters are calculated by the large cross-section theory and mode cut-off equation.The effect on reverse bias voltages in analysed by the doping concentration in n^+-Si.The is significant because the reverse bias increases sharply when the doped concentration in n^+-Si is less than 1×10^20cm^-3.     

Silicon photomultipliers for radioactive waste online monitoring

A prototype demonstrator for the online monitoring of short-medium term radioactive waste repositories is currently under development at INFN-LNS. Such a system is planned to be distributed, fine-grained, robust, reliable, and based on low-cost components. With the main purpose of counting gamma radiation, we implemented a new kind of mini-detector based on silicon photomultipliers and scintillating fibers that behaves like a cheap scintillating Geiger-Muller counter and is suitable to be deployed in the shape of a grid around waste drums.     

开路p－n结对近邻光电二极管特性的影响

对ｐ－ｎ结邻近有大面积受光开路ｐ－ｎ结的光电特性进行了理论和实验分析。结果表明，这种结构不能改善光敏器件的灵敏度和探测率，而且由于大面积受光开路ｐ－ｎ结的存在，器件的灵敏度和探测率比相同面的单个ｐ－ｎ结小。     

A six-degree-of-freedom measurement system for the motion accuracy of linear stages

This paper presents a new six-degree-of-freedom measurement system (6DMS) which has the capability to measure simultaneously all six motion errors of a linear stage. This system employs three parallel laser beams to detect three relative linear distances of a moving body by Doppler effect so that the positioning, yaw and pitch errors can be separated. With an additional beam splitter and two quadrant photodetectors to detect the lateral shifts of the returned beams, the remaining two straightness errors and roll error can be obtained at the same time. In comparison with the HP5528A system, the accuracy of the positioning error is about 0.01 μm to the range of 10 m, the straightness error is about 1 μm within the measuring range of ± 0.1 mm, and angular errors are all about 1 arcsec within the range of ± 50 arcsecs. This system is simple in principle and can be easily equipped to any moving stages, such as linear stages, X-Y tables, CMMs, and machine tools.     

Voltage-tunable dual-band infrared photodetectors with Si/SiGe metal-semiconductor-metal heterostructure

A simple and low-cost structure of voltage-tunable dual-band near-infrared photodetector (PD) has been proposed, in which the PDs were developed by using Si_0.8Ge_0.2/Si metal-semiconductor-metal (MSM) heterostructure. The Si_0.8Ge_0.2/Si layers were deposited by ultrahigh-vacuum chemical vapor deposition system and a transparent layer of indium-tin oxide (ITO) was used as a metal layer to enhance the entrance of photons. In this study, we found that only one band was detected with a peak wavelength located at 950 nm at zero applied bias. When bias was increased to 1 V, in contrast a dual-band was achieved, where two peak wavelengths were centered at 950- and 1150-nm. It is suggested that the two bands are the absorption of top-Si and bottom-Si_0.8Ge_0.2 layers, respectively. The spectra of Si bulk and Si_0.8Ge_0.2 layer were also measured to verify our results and relating mechanisms are explained here.     

Carbon nanotube-based heterostructures for high-performance photodetectors: Recent progress and future prospects

Unique optical, electrical and chemical properties make carbon nanotubes (CNTs) an excellent candidate for potential applications in the next-generation optoelectronics. Especially, the optoelectronic properties of CNTs can be enhanced dramatically by constructing heterostructures with other materials, in which the charge separation efficiency is enhanced and the recombination probability of excitons is suppressed significantly. Therefore, the CNT-based heterostructures have been widely used as active materials in high-performance photoelectronic devices. Herein, the recent progress of the CNT-based heterostructure photodetectors is reviewed. Firstly, the working mechanisms and typical figures-of-merits are introduced. Secondly, different type CNT-based heterostructures and related photodetectors are highlighted, such as van der Waals heterostructures, all-carbon heterostructures, and bulk heterostructures. Finally, we give the current challenges and future prospects for the development of this emerging field.