An equivalent circuit model for the long-wavelength quantum well infrared photodetectors

We present an equivalent circuit model for AlGaAs/GaAs long wavelength quantum well infrared photodetectors (LW-QWIPs). Bias dependence of the dark current and photoresponse is described with the aid of analogue circuit modeling technique in the TINA software. This model can be integrated with the readout circuit for the whole device circuit simulation and optimization further. The designed parameters of the LW-QWIPs can be fed into this model as user-defined circuit parameters to simulate the detector performance. The obtained results are consistent with the experimental measurements.     

HOT infrared photodetectors

At present, uncooled thermal detector focal plane arrays are successfully used in staring thermal imagers. However, the performance of thermal detectors is modest, they suffer from slow response and they are not very useful in applications requiring multispectral detection. Infrared (IR) photon detectors are typically operated at cryogenic temperatures to decrease the noise of the detector arising from various mechanisms associated with the narrow band gap. There are considerable efforts to decrease system cost, size, weight, and power consumption to increase the operating temperature in so-called high-operating-temperature (HOT) detectors. Initial efforts were concentrated on photoconductors and photoelectromagnetic detectors. Next, several ways to achieve HOT detector operation have been elaborated including non-equilibrium detector design with Auger suppression and optical immersion. Recently, a new strategies used to achieve HOT detectors include barrier structures such as nBn, material improvement to lower generation-recombination leakage mechanisms, alternate materials such as superlattices and cascade infrared devices. Another method to reduce detector’s dark current is reducing volume of detector material via a concept of photon trapping detector. In this paper, a number of concepts to improve performance of photon detectors operating at near room temperature are presented. Mostly three types of detector materials are considered — HgCdTe and InAsSb ternary alloys, and type-II InAs/GaSb superlattice. Recently, advanced heterojunction photovoltaic detectors have been developed. Novel HOT detector designs, so called interband cascade infrared detectors, have emerged as competitors of HgCdTe photodetectors.     

Long wavelength photodetectors

The role of long wavelength systems (1.0μm<λ< 10.0μm) in fiber optics communications is evaluated. For high-bit rate optical telecommunications at 1.3 μm or 1.5 μm, GaInAs p-i-n detectors have emerged as the preferred choice because of their low noise, excellent sensitivity, and high temperature stability. Ge and HgCdTe photodiodes offer nearly equivalent performance and a somewhat more advanced production technology. Beyond 2 μm, HgCdTe would seem to be the clear choice for photodetector applications. Avalanche photodiodes in long wavelength optical fiber links may find uses in situations involving high bit rate transmission using low cost components. Although avalanche gain will always improve the system sensitivity, the LED/APD combination is only half as sensitive as a laser/p-i-n system, as well as being bandwidth limited. Nontelecommunications applications involving data base and fiber guidance systems are discussed, and a prospective look is taken at the uses, such as power transmission, of ultra low-loss fibers in the 2 to 10 μm region of the optical spectrum.     

Ultrafast photodetectors and receiver

A family of ultrafast photodetectors and photoreceivers, based on evanescently coupled photodiodes, is described. The waveguide-integrated detectors are monolithically integrated with HEMTs, employing semi-insulating optical waveguides on a semi-insulating InP:Fe substrate. The integration scheme is explained and demonstrated by several examples of broadband and narrowband photodetectors, balanced detectors and photoreceivers, focussing on applications at data rates from 80 to ∼160 Gbit/s.     

Scalable silicon nanowire photodetectors

This paper presents photodetectors having vertically stacked electrodes with sub-micron (300 nm) separation based on silicon nanowire (SiNW) nanocomposites. The thin-film-like devices are made using standard photolithography instead of electron beam lithography and thus are amenable to scalable low-cost manufacturing. The processing technique is not limited to SiNWs and can be extended to different nanowires (NWs) (e.g., ZnO, CdSe) and substrates. The current–voltage characteristics show Schottky behaviour that is dependent on the properties of the contact metal and that of the pristine SiNWs. This makes these devices suitable for examination of electronic transport in SiNWs. Preliminary results for light sensitivity show promising photoresponse that is a function of effective NW density.     

Interaction of long-wavelength excitations in crystals

The conditions of resonance interaction of phonons for a scalar model of a crystal in the region of the initial linear section of the dispersion curve of acoustic phonons are investigated using two-particle Green's functions. Fiz. Tverd. Tela (St. Petersburg) 41, 130–133 (January 1999)     

Low-temperature performance of InP-based long-wavelength VCSELs

We have studied, for the first time, the parameters of long-wavelength InP-based buried tunnel junction (BTJ) VCSELs with substrate temperature varied in the range between 150 and 330 K. The BTJ-VCSELs with threshold currents <1 mA were designed by VERTILAS (Germany) to operate near 1512 nm and 1577 nm at room temperature (models VL-1512 and VL-1577, respectively). Reducing the substrate temperature of the lasers from room temperature to 150 K resulted in more than a fourfold increase of the threshold injection current accompanied with threefold and twofold increases in output power and slope efficiency, respectively. We have observed continuous single-mode tuning over intervals up to ∼20 nm (VL-1512) and ∼22 nm (VL-1577) at constant injection currents and substrate temperatures varied in a 180 K range. The emission wavelength was found to shift linearly with temperature with rates of 0.11 nm/K and 0.12 nm/K for lasers VL-1512 and VL-1577, respectively. The single-mode laser output reached ∼3 mW for both lasers cooled down to 173 K. Gas sensors based on BTJ-VCSELs can be temperature tuned over wide spectral intervals using either a cooler or a low ambient temperature to control laser substrate temperature. Ultra-sensitive gas concentration measurements under low ambient temperatures may include chemical analysis of the lower earth stratosphere and of the martian atmosphere. PACS 42.55.Px; 42.62.Fi; 39.30.+w     

Interband damping of long-wavelength bulk plasmons

The contribution of interband transitions of electrons to the damping of plasma oscillations in a metal is investigated in the long-wavelength limit using two different approximation schemes: (i) a method using sum rules and (ii) a perturbative approach. We show that the first method leads to unphysical results, but the perturbation theory is justified for those metals in which the lattice periodicity can be represented by a weak pseudopotential. The numerical value of damping is computed for aluminium. The calculated frequency dependence of the imaginary part of the dielectric constant of Al is shown to be in good agreement with the same curve obtained from optical data.     

光伏型太赫兹量子阱探测器研究进展

光伏型太赫兹量子阱探测器(PV-THzQWIP)是光伏型量子阱光电探测器(PV-QWIP)在THz波段的扩展,它具有功耗低、暗电流小、噪声水平低以及焦平面阵列(FPAs)热分辨率高等优点,是THz频段技术应用的重要器件之一.文章主要介绍了PV-THzQWIP的工作原理、特点、理论设计及其研究进展.     

Graphene-based heterojunction for enhanced photodetectors

Graphene has high light transmittance of 97.7% and ultrafast carrier mobility, which means it has attracted widespread attention in two-dimensional materials. However, the optical absorptivity of single-layer graphene is only 2.3%, and the corresponding photoresponsivity is difficult to produce at normal light irradiation. And the low on—off ratio resulting from the zero bandgap makes it unsuitable for many electronic devices, hindering potential development. The graphene-based heterojunction composed of graphene and other materials has outstanding optical and electrical properties, which can mutually modify the defects of both the graphene and material making it then suitable for optoelectronic devices. In this review, the advantages of graphene-based heterojunctions in the enhancement of the performance of photodetectors are reviewed. Firstly, we focus on the photocurrent generation mechanism of a graphene-based heterojunction photodetector, especially photovoltaic, photoconduction and photogating effects. Secondly, the classification of graphene-based heterojunctions in different directions is summarized. Meanwhile, the latest research progress of graphene-transition metal dichalcogenide (TMD) heterojunction photodetectors with excellent performance in graphene-based heterostructures is introduced. Finally, the difficulties faced by the existing technologies of graphene-based photodetectors are discussed, and further prospects are proposed.     

Gaseous photodetectors with solid photocathodes

Remarkable properties of gas photodetectors make them attractive for application in high energy physics, astrophysics, and medical imaging. This review presents the results of research and development of gaseous photodetectors with solid photocathodes (GPDs). In particular, efficient photocathodes for the ultraviolet (mainly CsI) and the visible ranges, including photocathodes with protective dielectric nanofilms, are described. Some problems of the physics of gaseous photodetectors and photocathodes are considered: photoelectron backscattering in gas, photoemission amplification in an electric field, photoelectron transport through nanofilms, protective properties of nanofilms, and photon and ion feedback. A separate section is devoted to GPDs based on gas electron multipliers (GEMs), including sealed GPDs and cryogenic two-phase avalanche detectors with CsI photocathodes.     

光伏型太赫兹量子阱探测器研究进展

光伏型太赫兹量子阱探测器(PV-THzQWIP)是光伏型量子阱光电探测器(PV-QWIP)在THz波段的扩展,它具有功耗低、暗电流小、噪声水平低以及焦平面阵列(FPAs)热分辨率高等优点,是THz频段技术应用的重要器件之一.文章主要介绍了PV-THzQWIP的工作原理、特点、理论设计及其研究进展.     

Uncooled infrared photodetectors in Poland

The history and present status of the middle and long wavelength Hg_1-xCd_xTe infrared detectors in Poland are reviewed. Research and development efforts in Poland were concentrated mostly on uncooled market niche. Technology of the infrared photodetectors has been developed by several research groups. The devices are based on mercury-based variable band gap semiconductor alloys. Modified isothermal vapour phase epitaxy (ISOVPE) has been used for many years for research and commercial fabrication of photoconductive, photoelectromagnetic and other devices. Bulk growth and liquid phase epitaxy was also used. At present, the fabrication of IR devices relies on low temperature epitaxial technique, namely metalorganic vapour phase deposition (MOCVD), frequently in combination with the ISOVPE. Photoconductive and photoelectromagnetic detectors are still in production. The devices are gradually replaced with photovoltaic devices which offer inherent advantages of no electric or magnetic bias, no heat load and no flicker noise. Potentially, the PV devices could offer high performance and very fast response. At present, the uncooled long wavelength devices of conventional design suffer from two issues; namely low quantum efficiency and very low junction resistance. It makes them useless for practical applications. The problems have been solved with advanced 3D band gap engineered architecture, multiple cell heterojunction devices connected in series, monolithic integration of the detectors with microoptics and other improvements. Present fabrication program includes devices which are optimized for operation at any wavelength within a wide spectral range 1–15 μm and 200–300 K temperature range. Special solutions have been applied to improve speed of response. Some devices show picoseconds range response time. The devices have found numerous civilian and military applications. The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570K (2005).     

光栅局域调控二维光电探测器

近年来,二维材料独特的物理、化学和电子特性受到了越来越多的科研人员的关注.特别是石墨烯、黑磷和过渡金属硫化物等二维材料具有优良的光电性能和输运性质,使其在下一代光电子器件领域具有广阔的应用前景.本文将主要介绍二维材料在光电探测领域上的应用优势,概述光电探测器的基本原理和参数指标,重点探讨光栅效应与传统光电导效应的区别,...     

Single-shot cross-correlator using a long-wavelength sampling pulse

We present a single-shot cross-correlating scheme capable of high dynamic range and large temporal window for pulse contrast characterization. By adopting a long-wavelength sampling pulse parametrically converted from the pulse under test, wavelength combination in the correlating process allows the use of a large noncollinear phase-matching angle in periodically poled lithium niobate crystal, matches the high-sensitivity detection system consisting of a fiber array and a photomultiplier tube, and favors the elimination of optical scattering noise. The prototype experiments demonstrate a detectable contrast maximum up to ～10(9), temporal window of ～50?ps, and resolution of ～1?ps, using <0.5?mJ input energy.