Showing papers on "Responsivity published in 2000"
TL;DR: In this article, the authors report the fabrication and characterization of AlxGa1−xN photodiodes (x∼0.70) grown on sapphire by low-pressure metalorganic chemical vapor deposition.
Abstract: We report the fabrication and characterization of AlxGa1−xN photodiodes (x∼0.70) grown on sapphire by low-pressure metalorganic chemical vapor deposition. The peak responsivity for −5 V bias is 0.11 A/W at 232 nm, corresponding to an internal quantum efficiency greater than 90%. The device response drops four orders of magnitude by 275 nm and remains at low response for the entire near-ultraviolet and visible spectrum. Improvements were made to the device design including a semitransparent Ni/Au contact layer and a GaN:Mg cap layer, which dramatically increased device response by enhancing the carrier collection efficiency.
169 citations
TL;DR: In this paper, the fabrication and characterization of n-Al0.44Ga0.56N/p-GaN ultraviolet solar-blind photodetectors were reported.
Abstract: We report on the fabrication and characterization of n-Al0.44Ga0.56N/i-Al0.44Ga0.56N/p-GaN ultraviolet solar-blind photodetectors. The diodes were fabricated by organometallic vapor phase epitaxy on low-defect-density AlGaN layers using a low-temperature interlayer technique. They present a long cutoff wavelength at 270 nm with high rejection of solar light and a responsivity of 12 mA/W. Low dark currents between 4 and 35 pA/mm2 at -5 V have been measured. A photocurrent decay time of 14 µs has been estimated in unbiased diodes. Due to the large dynamic resistance of the diode at 0 V bias, the detector itself shows a detectivity of 1.2×1013 cmHz1/2W-1.
120 citations
TL;DR: In this paper, a laser-based facility has been developed to provide high-flux, monochromatic, Lambertian radiation over the spectral range 0.2 µm to 18 µm.
Abstract: A laser-based facility has been developed to provide high-flux, monochromatic, Lambertian radiation over the spectral range 0.2 µm to 18 µm. The facility was designed to reduce the uncertainties in a variety of radiometric applications, including irradiance and radiance responsivity calibrations. The operational characteristics of the facility are discussed and the results of detector responsivity calibrations over the spectral range 0.406 µm to 0.920 µm are presented.
117 citations
TL;DR: In this paper, a CMOS active pixel sensor has been evaluated with Co60, 10 MeV proton and heavy ion irradiation, and permanent displacement damage effects were seen but total ionizing dose-induced dark current and increase in power supply current annealed at 100/spl deg/C.
Abstract: A CMOS active pixel sensor has been evaluated with Co60, 10 MeV proton and heavy-ion irradiation. Permanent displacement damage effects were seen but total ionizing dose-induced dark current and increase in power supply current annealed at 100/spl deg/C. Large changes in responsivity were seen after proton irradiation, which subsequently annealed. Mechanisms for these responsivity changes are discussed, but a definitive cause has not yet been established.
116 citations
TL;DR: In this paper, the influence of material properties on device parameters is discussed, and the analysis considers front and back illumination and distinguishes between devices fabricated on ideal high-quality material and state-of-the-art heteroepitaxial AlxGa1−xN.
Abstract: Schottky barrier photovoltaic detectors have been fabricated on n-AlxGa1−xN(0⩽x⩽0.35) and p-GaN epitaxial layers grown on sapphire. Their characteristics have been analyzed and modeled, in order to determine the physical mechanisms that limit their performance. The influence of material properties on device parameters is discussed. Our analysis considers front and back illumination and distinguishes between devices fabricated on ideal high-quality material and state-of-the-art heteroepitaxial AlxGa1−xN. In the former case, low doping levels are advisable to achieve high responsivity and a sharp spectral cutoff. The epitaxial layer should be thin (<0.5 μm) to optimize the ultraviolet/visible contrast. In present devices fabricated on heteroepitaxial AlxGa1−xN, the responsivity is limited by the diffusion length. In this case, thick AlxGa1−xN layers are advisable, because the reduction in the dislocation density results in lower leakage currents, larger diffusion length, and higher responsivity. In order to...
104 citations
TL;DR: In this paper, the authors used an AlGaN-based photodiodes using an inverted heterostructure photodiode design, which utilizes an AlxGa1−xN(x>03) intrinsic or lightly doped active layer surrounded by p-and/or n-type contact layers having a narrower band gap than the active layer.
Abstract: True solar-blind operation with a sharp responsivity cutoff at ∼300 nm has been demonstrated in AlGaN-based photodiodes using an “inverted heterostructure photodiode” design This structure utilizes an AlxGa1−xN(x>03) intrinsic or lightly doped active layer surrounded by p- and/or n-type contact layers having a narrower band gap than the active layer By utilizing narrow band gap (eg, GaN) contact layers, the difficulties associated with achieving high doping efficiencies in wide band gap contact layers are circumvented This basic structure is applicable to both front- and back-side illuminated detector geometries Front-side illuminated solar-blind photodiodes were demonstrated with a peak responsivity of 008 A/W at 285 nm, while back-side illuminated detectors yielded a peak responsivity of 0033 A/W at 275 nm (both are measured without antireflection coating) Both types of detectors offered sharp spectral responsivity cutoff of at least three orders of magnitude by 325 nm
90 citations
TL;DR: In this paper, an epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature.
Abstract: Epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature. Continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3 grown by the pulsed laser deposition technique were found to possess superior performance regarding the maximum of temperature coefficient of resistivity (TCR) @300 K. In these films phase transition temperature Tc ranges from 266 to 327 K. We have engineered the film of the optimum composition x=0.37 exhibiting the maximum of TCR=7.4% K−1 @295 K. Relatively low excess noise (normalized value γ/n of 3×10−21 cm3) has been achieved due to the epitaxial quality of the fabricated film. Using this film, infrared radiation bolometer demonstrator, operating at room temperature, has been built and tested. The bolometer resolves the noise equivalent temperature difference as low as 120 nK/Hz and shows signal-to-noise ratio SNR=8×106 Hz/K, responsivity R=0.6 V/W, detectivity D=0.9×107 cmHz/W, and noise equivalent power NEP=3×10−8 WHz at 30 Hz frame frequency. For micromachined thermally isolated La0.7(Pb0.63Sr0.37)0.3MnO3 thin-film bolometer one can expect to get responsivity about 4×103 V/W and detectivity higher than 109 cmHz/W @30 Hz.
86 citations
TL;DR: In this paper, the authors present performance measurements of fiber-optic flexural disk accelerometers and find that a complicated compromise between all of these design parameters is required to achieve the optimum performance.
Abstract: This paper presents performance measurements of fiber-optic flexural disk accelerometers. The flexural disk acts as a mass-spring element to which the fiber is bonded, such that an acceleration causes a strain to be imposed on the fiber which is measured interferometrically. Simple analytical models have been written to calculate the responsivity and resonant frequency of disks under various boundary conditions and the results of the models have been shown to be in good agreement with the measured responsivity for the case of moderately thick disks. Six optical fiber accelerometers based on flexural disks of different thickness and supports have been demonstrated to exhibit a responsivity in the range from 28 to 39 dB re 1 rad/g with a resonant frequency between 2.4 kHz to greater than 5 kHz, respectively. Of the designs considered, the centrally supported disk is shown to give the highest combination of responsivity and bandwidth. A centrally supported disk has been demonstrated to exhibit a flat response up to 2 kHz and a responsivity of 37 dB re 1 rad/g which when combined with an interferometric phase resolution of 6 /spl mu/rad//spl radic/Hz, would give a minimum detectable acceleration of 84 ng//spl radic/Hz. We have attempted to cover all aspects of the sensor design including responsivity, bandwidth, cross-responsivity, phase response and size and find that a complicated compromise between all of these design parameters is required to achieve the optimum performance.
72 citations
Patent•
10 Aug 2000TL;DR: In this article, a novel combination of integrated MEMS and photonics was used to achieve high IR detection sensitivity with low noise, where photons are being modulated instead of electrons.
Abstract: A MicroOptoElectroMechanical (MOEM) IR detector utilizes a novel combination of integrated MEMS and photonics to achieve high responsivity with low noise. Increasing incident radiant energy bends a bimaterial arm that moves a coupling waveguide into the evanescent field of a principal optical waveguide. This, in turn, modulates the light in the principal waveguide. This device has high detection sensitivity to incident radiation due to the combination of the length of the lever arm and the sensitivity of the evanescent field. The device exhibits low noise because photons are being modulated instead of electrons.
72 citations
TL;DR: In this paper, the GaN epitaxial layers were grown on Si substrates by means of metalorganic chemical-vapor deposition and the response time of 4.8 ms was determined by measurements of photocurrent versus modulation frequency.
Abstract: GaN metal–semiconductor–metal photoconductive detectors have been fabricated on Si(111) substrates. The GaN epitaxial layers were grown on Si substrates by means of metalorganic chemical-vapor deposition. These detectors exhibited a sharp cutoff at the wavelength of 363 nm and a high responsivity at a wavelength from 360 to 250 nm. A maximum responsivity of 6.9 A/W was achieved at 357 nm with a 5 V bias. The relationship between the responsivity and the bias voltage was measured. The responsivity saturated when the bias voltage reached 5 V. The response time of 4.8 ms was determined by the measurements of photocurrent versus modulation frequency.
71 citations
TL;DR: In this paper, a novel technique that drastically reduces the self-heating effect in microbolometers and which can be used to enhance the response due to infrared (IR) was demonstrated.
Abstract: This paper experimentally demonstrates a novel technique that drastically reduces the self-heating effect in microbolometers and which can be used to enhance the response due to infrared (IR). This is accomplished by using two bolometers with tailored thermal parameters, in particular, similar thermal mass but different thermal conductivity. Test devices with responsivity of over 6000 V/W at bias voltage of 3 V have been fabricated. Results indicate that this method is robust even under considerable mismatch of device parameters. We believe that this technique would pave way for realization of relatively simple, low cost and sensitive IR detectors for use in thermometry, imaging and other IR applications.
TL;DR: In this article, photovoltaic quantum-dot infrared detectors fabricated from (In, Ga)As/GaAs heterostructures were demonstrated and achieved a peak detectivity of 2×108 cm 1/2/W with a responsivity of 1 mA/W at a wavelength of 13 μm.
Abstract: We demonstrate the operation of photovoltaic quantum-dot infrared detectors fabricated from (In, Ga)As/GaAs heterostructures. These detectors are sensitive to normal incidence light. At zero bias, we obtain a low-temperature (78 K) peak detectivity of 2×108 cm Hz1/2/W, with a responsivity of 1 mA/W at a wavelength of 13 μm for one of the devices. The photovoltaic effect in our detectors is a result of the intrinsic inversion asymmetry of the band structure of self-formed quantum dots. A compensation voltage of 18 mV is measured.
TL;DR: In this article, a very long wavelength infrared detector based on InAs/GaSb superlattices operating at T=80 K was demonstrated. But this detector was not suitable for the detection of very long wavelengths.
Abstract: We report a demonstration of very long wavelength infrared detectors based on InAs/GaSb superlattices operating at T=80 K. Detector structures with excellent material quality were grown on an optimized GaSb buffer layer on GaAs semi-insulating substrates. Photoconductive devices with 50% cutoff wavelength of λc=17 μm showed a peak responsivity of about 100 mA/W at T=80 K. Devices with 50% cutoff wavelengths up to λc=22 μm were demonstrated at this temperature. Good uniformity was obtained over large areas even for the devices with very long cutoff wavelengths.
TL;DR: In this article, a GaAs/InGaAs far-infrared quantum well photodetectors based on a bound-to-continuum intersubband transition with a (zero response) cutoff wavelength of 35 μm are reported.
Abstract: GaAs/InGaAs far-infrared quantum well photodetectors based on a bound-to-continuum intersubband transition with a (zero response) cutoff wavelength of 35 μm are reported. A peak responsivity of 0.45 A/W and detectivity of 6.0×109 cmHz/W at a wavelength of 31 μm and a temperature of 4.2 K have been experimentally achieved. Infrared response was observed at temperatures up to 18 K. A calculated responsivity spectrum using a bound-to-continuum line shape corrected for phonon absorption is fitted to the experimental response. The calculated line shape without absorption gives a cutoff wavelength of 38 μm with a peak responsivity of 0.50 A/W and a detectivity of 6.6×109 cmHz/W at 32 μm.
TL;DR: In this article, a far-infrared detector made of self-assembled quantum dots embedded in the channel region of modulation-doped heterostructures is demonstrated at room temperature and 80 K, achieving a peak responsivity of 5.3 A/W at 9.0 /spl mu/m.
Abstract: Room temperature operation of far-infrared detectors made of self-assembled quantum dots embedded in the channel region of modulation-doped heterostructures is demonstrated. At room temperature, the detector shows a low dark current ranging in the nano-amperes at a bias voltage of 10 V. After the optimization of the separation between the quantum dot region and the 2DEG, a peak responsivity of 5.3 A/W is obtained at 9.0 /spl mu/m. The high detectivities of 6/spl times/10/sup 8/ and 5/spl times/10/sup 10/ cmHz/sup 1/2//W are obtained at room temperature and 80 K, respectively.
TL;DR: An InAs0.89Sb0.11 photovoltaic detector that operates at room temperature in the 2.5-5 mu m mid-infrared wavelength region is reported in this paper.
Abstract: An InAs0.89Sb0.11 photovoltaic detector that operates at room temperature in the 2.5-5 mu m mid-infrared wavelength region is reported. The photodiode has an extended spectral response compared with other currently available III-V room-temperature detectors. In order to accommodate the large lattice mismatch between the InAs0.89Sb0.11 active region and the InAs substrate, a buffer layer with an intermediate composition was introduced into the structure. In this way, we obtained room-temperature photodiodes with a cutoff wavelength near 5 mu m, a peak responsivity of 0.8 A/W, and a detectivity of 1.26 x 10(9) cm Hz(1/2)/W. These devices could be effectively used as the basis of an optical sensor for the environmental monitoring of carbon monoxide at 4.6 mu m, or as a replacement for PbSe photoconductors. (C) 2000 American Institute of Physics. [S0003-6951(00)02332-9].
TL;DR: A backside-illuminated solar-blind UV detector based on an AlGaN p-i-n heterostructure has been successfully synthesized, fabricated and tested as discussed by the authors.
Abstract: A backside-illuminated solar-blind UV detector based on an AlGaN p-i-n heterostructure has been successfully synthesized, fabricated and tested. The p-i-n photodiode structure consists of a 1.0 μm n-type Al0.64Ga0.36N:Si layer grown by MOVPE onto a low temperature AlN buffer layer on a polished sapphire substrate. On top of this base layer is a 0.2 μm undoped Al0.47Ga0.53N active layer and a 0.5 μm p-type Al0.47Ga0.53N:Mg top layer. Square mesas of area A = 4 × 10−4 cm2 were obtained by reactive ion etching using BCl3. The solar-blind photodiode exhibits a very narrow UV spectral responsivity band peaked at 273 nm with a FWHM = 21 nm. Maximum responsivity R = 0.051 A/W at 273 nm, corresponding to an internal quantum efficiency of 27%. R0A values up to 8 × 107Ω-cm2 were obtained, corresponding to D* = 3.5 × 1012 cm Hz1/2W−1 at 273 nm.
TL;DR: In this article, the performance of a Pb1−xSnxTe(In) photodetector was compared with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity.
Abstract: We have compared directly the performance of a Pb1−xSnxTe(In) photodetector with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity. The Pb1−xSnxTe(In) photodetector has current responsivity SI several orders of magnitude higher than the Si(Sb) BIB at wavelength λ=14.5 μm. Persistent photoresponse with SI∼103 A/W at 40 mV bias and 1 s integration time at the wavelengths λ=90 and 116 μm has also been observed in the Pb1−xSnxTe(In) photodetector. This is larger by a factor of ∼100 than the responsivity of the Ge(Ga) photoconductor in the same conditions.
TL;DR: In this paper, a 16-pixel linear array with a photoresponse of about 650 ps and an enhancement of responsivity by a factor of four is presented, where the active layer is a thermally evaporated polycrystalline germanium.
Abstract: The fabrication and characterization of near infrared photodetectors integrated on silicon substrates are reported on where the active layer is a thermally evaporated polycrystalline germanium. Recent results are presented in the effort to enhance the optoelectronic properties of the poly-Ge film in terms of uniformity for multiple device integration, speed and responsivity. In particular we demonstrate a 16 pixel linear array, a speed of photoresponse of about 650 ps and an enhancement of responsivity by a factor of four. The fabrication process, including substrate cleaning and preparation, requires temperatures lower than 300°C being fully compatible with silicon technology.
TL;DR: In this article, a visible-blind reach-through avalanche photodiodes (RAPDs) were designed and fabricated with mesa edge termination and thermal oxide passivation techniques.
Abstract: 4H-SiC visible-blind reach-through avalanche photodiodes (RAPDs) were designed and fabricated with mesa edge termination and thermal oxide passivation techniques. The devices show “hard” avalanche breakdown with a positive temperature coefficient. The photo response spectra, measured at different biases, displayed a maximum responsivity of 106 A/W, and a corresponding optical gain of about 500.
15 Dec 2000
TL;DR: In this paper, the authors reported a 320 x 240 uncooled IRFPA with 40 micrometers pitch having diode detectors fabricated on an SOI wafer and improved the infrared absorbing structure in the newly developed FPA.
Abstract: We reported a 320 x 240 uncooled IRFPA with 40 micrometers pitch having diode detectors fabricated on an SOI wafer. Since the fabrication process of the SOI diode detector is compatible with the silicon IC process, only a silicon IC fab is necessary for manufacture of the FPAs. This enables mass production of low cost uncooled FPAs. This paper focuses on the performance of the FPA. In the previous paper, we proposed a novel infrared absorbing structure which offers a very high fill factor. Although this structure exhibited a high infrared absorption because of interference absorbing components incorporated in the structure, large thermal capacitance was an issue. Thus we have improved the infrared absorbing structure in the newly developed FPA. The improved absorbing structure has been devised making use of reflection of metal interconnections including diode metal straps. A thermal time constant of 17 msec has been achieved without degrading the responsivity compared with the conventional absorbing structure.
TL;DR: In this article, a mesa type detector has high responsivity in the 1.4 to 2.4 /spl mu/m wavelength range with -0.3 V bias, 40 /spl µ/A dark current for a 1 mm diameter detector and the highest detectivity D* of 2.
Abstract: A molecular beam epitaxy grown GaInAsSb pin photodetector lattice matched to a GaSb substrate is reported. The mesa type detector has high responsivity in the 1.4 to 2.4 /spl mu/m wavelength range with -0.3 V bias, 40 /spl mu/A dark current for a 1 mm diameter detector and the highest detectivity D* of 2.6/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W reported for a GaInAsSb detector. The measured responsivity compares well with k/spl middot/p calculations.
TL;DR: In this article, the authors describe the growth, fabrication, and characterization of an ultraviolet (UV) photoconductive detector based on InxAlyGa1−x−yN quaternary alloy that is lattice matched to GaN.
Abstract: We describe the growth, fabrication, and characterization of an ultraviolet (UV) photoconductive detector based on InxAlyGa1−x−yN quaternary alloy that is lattice matched to GaN. The detector consisted of 0.1 μm InxAlyGa1−x−yN alloy grown on 0.5–1.0 μm GaN epilayer by metalorganic chemical vapor deposition. With varying indium concentration, the cut-off wavelength of the InxAlyGa1−x−yN detectors could be varied to the deep UV range. The most important and intriguing result is that the responsivity of the InxAlyGa1−x−yN quaternary alloy exceeded that of AlGaN alloy of a comparable cutoff wavelength by a factor of five. This makes the nitride quaternary alloy very important material for solar blind UV detectors applications particularly in the deep UV range where Al rich AlGaN alloys have problems with low quantum efficiency and cracks due in part to lattice mismatch with GaN. The advantages of InxAlyGa1−x−yN quaternary over AlGaN ternary alloys for UV detector applications are also discussed.
TL;DR: The first results obtained in the framework of the recently started Italian National Project ‘EUV Diamond Detectors’ are reported in this article, aimed at the development of fast stable visible-blind and highly sensitive UV photodetectors based on CVD diamond, suitable for laboratory and space applications.
TL;DR: In this paper, the Schottky barrier photodetectors based on Si-doped Al0.35Ga0.65N layers for solar UV-band monitoring (λ 104) and a responsivity of 5 mA/W at 257 nm are reached.
Abstract: We report on the fabrication and characterization of Schottky barrier photodetectors based on Si-doped Al0.35Ga0.65N layers grown on Si(111) substrates, for solar UV-band monitoring (λ 104) and a responsivity of 5 mA/W at 257 nm are reached. The detector time response is limited by the resistance×capacitance product, with a minimum time constant of 20 ns in the zero-load-resistance limit. After photodiode voltage breakdown, the effect on the detector response is discussed.
TL;DR: In this paper, a hot-electron bolometric detector and mixer, which uses the nonlinearities of the heated two-dimensional electron gas medium, is proposed and analyzed.
Abstract: A hot-electron bolometric detector and mixer (heterodyne detector), which uses the nonlinearities of the heated two-dimensional electron gas medium, is proposed and analyzed. The cooling process of the detector is through diffusion of the electrons into the contacts; a time constant of 1 ps and responsivity of 3000 V/W are calculated for a device which is 0.8 μm long. The predicted double-sideband receiver noise temperature for the mixer version is in the range 1000–2000 K at 1 THz, with a 100 GHz intermediate frequency bandwidth. The operating temperature would be 77 K and the local oscillator power 1 μW.
TL;DR: The improved quantum efficiency model can be accounted for completely by the adjustment of just one parameter, i.e., the collection efficiency near the SiO(2)/Si interface, and an explanation is proposed for the change in the spectral responsivity of silicon photodiodes that is due to UV radiation.
Abstract: We improve the methods used to interpolate the responsivity of unbiased silicon photodetectors in the near-ultraviolet region. This improvement is achieved by the derivation of an interpolation function for the quantum yield of silicon and by consideration of this function in the interpolation of the internal quantum efficiency of photodiodes. The calculated quantum-yield and spectral-responsivity values are compared with measurement results obtained by the study of a silicon trap detector and with values reported by other research groups. The comparisons show agreement with a standard deviation of 0.4% between our measured and modeled values for both the quantum yield and the spectral responsivity within the wavelength region from 260 to 400 nm. The proposed methods thus extend the predictability of the spectral responsivity of silicon photodetectors to the wavelength region from 260 to 950 nm. Furthermore, an explanation is proposed for the change in the spectral responsivity of silicon photodiodes that is due to UV radiation. In our improved quantum efficiency model the spectral change can be accounted for completely by the adjustment of just one parameter, i.e., the collection efficiency near the SiO2/Si interface.
07 Mar 2000
TL;DR: By monolithic integration of a spot size transformer, a responsivity of 0.5 A/W is achieved and fiber alignment tolerances are increased by one order of magnitude as discussed by the authors. But this method requires high bandwidth at high power levels, as supplied by waveguide-integrated p-i-n diodes on InP.
Abstract: 40 Gbit/s photodetectors require high bandwidth at high power levels, as supplied by waveguide-integrated p-i-n diodes on InP. By monolithic integration of a spot size transformer a responsivity of 0.5 A/W is achieved and fiber alignment tolerances are increased by one order of magnitude.
TL;DR: In this paper, a light-trap silicon radiometer was developed to hold the NIST spectral power and irradiance responsivity scales between 406 nm and 920 nm, which is built from replaceable input apertures and tightly packed different-size silicon photodiodes.
Abstract: A transmission-type light-trap silicon radiometer has been developed to hold the NIST spectral power and irradiance responsivity scales between 406 nm and 920 nm. The device is built from replaceable input apertures and tightly packed different-size silicon photodiodes. The photodiodes are positioned in a triangular shape tunnel such that beam clipping is entirely eliminated within an 8 field-ofview (FOV). A light trap is attached to the output of the radiometer to collect the transmitted radiation and to minimize the effect of ambient light. The photodiodes, selected for equal shunt resistance, are connected in parallel. The capacitance and the resultant shunt resistance of the device were measured and frequency compensations were applied in the feedback network of the photocurrent-to-voltage converter to optimize signal-, voltage-, and loop-gain characteristics. The trap radiometer can measure either dc or ac optical radiation with high sensitivity. The noise-equivalent-power of the optimized device is 47 fW in dc mode and 5.2 fW at 10 Hz chopping. The relative deviation from the cosine responsivity in irradiance mode was measured to be equal to or less than 0.02 % within 5 FOV and 0.05 % at 8 FOV. The trap-radiometer can transfer irradiance responsivities with uncertainties comparable to those of primary standard radiometers. Illuminance and irradiance meters, holding the SI units (candela, color- and radiance-temperature), will be calibrated directly against the transfer standard trap-radiometer to obtain improved accuracy in the base-units.
TL;DR: In this paper, a novel monolithic distributed traveling wave photodetector with parallel optical feed to an array of individual photodiodes using an integrated multimode interference coupler was presented.
Abstract: We report on a novel monolithic distributed traveling wave photodetector with parallel optical feed to an array of individual photodiodes using an integrated multimode interference (MMI) coupler to attain high saturation current. The parallel optical feed reduces the maximum photocurrent and photocurrent density seen by any single photodiode, thus increasing the maximum linear photocurrent of the detector. We have successfully fabricated a device with a maximum linear photocurrent of 20 mA and a responsivity of 0.13 A/W.