Showing papers on "Responsivity published in 2007"
TL;DR: A Ge p-i-n photodetector that is monolithically integrated with silicon oxynitride and silicon nitride waveguides, which facilitates the integration with CMOS circuits.
Abstract: Photonic systems based on complementary metal oxide semiconductor (CMOS) technology require the integration of passive and active photonic devices. The integration of waveguides and photodetector is one of the most important technologies. We report a Ge p-i-n photodetector that is monolithically integrated with silicon oxynitride and silicon nitride waveguides. All processes and materials are CMOS compatible and can be implemented in the current integrated circuit process technology. The small size of the devices results in low absolute dark current. The waveguide-coupled Ge devices show high efficiency (~90%) over a wide range of wavelengths well beyond the direct band gap of Ge, resulting in a responsivity of 1.08 A/W for 1550 nm light. The device speed of 7.2 GHz at 1V reverse bias is strongly affected by the capacitance of the probe pads. The high-performance of the devices at low voltage (≤ 1V) facilitates the integration with CMOS circuits.
465 citations
TL;DR: Evanescently coupled Ge waveguide photodetectors that are grown on top of Si rib waveguides that have an optical bandwidth of 31.3 GHz at -2V for 1550nm are reported on.
Abstract: We report on evanescently coupled Ge waveguide photodetectors that are grown on top of Si rib waveguides. A Ge waveguide detector with a width of 7.4mum and length of 50 mum demonstrated an optical bandwidth of 31.3 GHz at -2V for 1550nm. In addition, a responsivity of 0.89 A/W at 1550 nm and dark current of 169 nA were measured from this detector at -2V. A higher responsivity of 1.16 A/W was also measured from a longer Ge waveguide detector (4.4 x 100 mum2), with a corresponding bandwidth of 29.4 GHz at -2V. An open eye diagram at 40 Gb/s is also shown.
401 citations
TL;DR: Design, fabrication and characterization of germanium on silicon photodetector integrated in SOI waveguide are reported, and a responsivity of 1 A/W and a -3 dB bandwidth of 25 GHz under 6 V bias have been obtained.
Abstract: We report the experimental demonstration of a germanium metal-semiconductor-metal (MSM) photodetector integrated in a SOI rib waveguide. Femtosecond pulse and frequency experiments have been used to characterize such photodetectors. The measured bandwidth under 6V bias is about 25 GHz at 1.55 µm wavelength with a responsivity as high as 1 A/W. The used technological processes are compatible with complementary-metal-oxide-semiconductor (CMOS) technology.
214 citations
TL;DR: A waveguide photodetector utilizing a hybrid waveguide structure consisting of AlGaInAs quantum wells bonded to a silicon waveguide that has a fiber coupled responsivity of 0.31 A/W and an internal quantum efficiency over the 1.5 mum wavelength range.
Abstract: We report a waveguide photodetector utilizing a hybrid waveguide structure consisting of AlGaInAs quantum wells bonded to a silicon waveguide. The light in the hybrid waveguide is absorbed by the AlGaInAs quantum wells under reverse bias. The photodetector has a fiber coupled responsivity of 0.31 A/W with an internal quantum efficiency of 90 % over the 1.5 mum wavelength range. This photodetector structure can be integrated with silicon evanescent lasers for power monitors or integrated with silicon evanescent amplifiers for preamplified receivers.
197 citations
TL;DR: In this article, a high performance 4H-SiC p-i-n photodetector for visible-blind ultraviolet (UV) applications has been designed and fabricated.
Abstract: A high-performance 4H-SiC p-i-n photodetector for visible-blind ultraviolet (UV) applications has been designed and fabricated. The electrical and optical characteristics were measured at room temperature. The photodetector suffered from significant dark current of 2.5 pA/mm2 at reverse bias of 5 V, and the UV light photocurrent was larger than four orders of magnitude higher than the dark current. The built-in potential and the unintentional i-layer doping concentration were obtained from capacitance-voltage (C-V) measurements. The spectral peak responsivity of the detector reached 0.13 A/W at a wavelength of 270 nm, corresponding to a maximum external quantum efficiency of ∼61%. And the ratio of responsivity at 270 nm to that at 380 nm was >103. The characteristics imply that the photodetector has a great improved ultraviolet-visible rejection ratio which is needed for ultraviolet signal detection.
183 citations
TL;DR: In this article, a nanocrysal TiO2 thin film was prepared by sol-gel method and was then used to fabricate metal-semiconductor-metal ultraviolet photodetectors with Au Schottky contact.
Abstract: Nanocrystalline TiO2 thin films were prepared by sol-gel method and were then used to fabricate metal-semiconductor-metal ultraviolet photodetectors with Au Schottky contact. It was found that dark current of the fabricated devices was only 1.9nA at 5V applied bias. High responsivity of 199A∕W was achieved when it was irradiated by the ultraviolet light (λ=260nm). The low dark current and high responsivity maybe attributed to the effect of Schottky barrier in company with neutral semiconductor owing to the wide finger gap of 20μm. The devices show a slow time response with a rise time of 6s and a decay time of 15s. The authors deduced that the slow time response was caused by defect traps which were widely distributed in nanocrysal.
177 citations
TL;DR: The p-i-n photodiode waveguide as discussed by the authors consists of an intrinsic waveguide 500 times250 nm where the optical mode is confined and two thin, 50nm-thick, doped Si wings that extend 5 mum out from either side of the waveguide.
Abstract: Submicrometer silicon photodiode waveguides, fabricated on silicon-on-insulator substrates, have photoresponse from <1270 to 1740 nm (0.8 AW-1 at 1550 nm) and a 3-dB bandwidth of 10 to 20 GHz. The p-i-n photodiode waveguide consists of an intrinsic waveguide 500times250 nm where the optical mode is confined and two thin, 50-nm-thick, doped Si wings that extend 5 mum out from either side of the waveguide. The Si wings, which are doped one p-type and the other n-type, make electric contact to the waveguide with minimal effect on the optical mode. The edges of the wings are metalized to increase electrical conductivity. Ion implantation of Si+ 1times10 13 cm-2 at 190 keV into the waveguide increases the optical absorption from 2-3 dBmiddotcm-1 to 200-100 dBmiddotcm-1 and causes the generation of a photocurrent when the waveguide is illuminated with subbandgap radiation. The diodes are not damaged by annealing to 450 degC for 15 s or 300 degC for 15 min. The photoresponse and thermal stability is believed due to an oxygen stabilized divacancy complex formed during ion implantation
175 citations
TL;DR: In this paper, a room temperature operating InAs quantum-dot infrared photodetector was reported, which achieved a detectivity of 2.8×1011cmHz1∕2∕W at 120K and a bias of −5V with a peak detection wavelength around 4.1μm and a quantum efficiency of 35%.
Abstract: The authors report a room temperature operating InAs quantum-dot infrared photodetector grown on InP substrate. The self-assembled InAs quantum dots and the device structure were grown by low-pressure metal-organic chemical vapor deposition. The detectivity was 2.8×1011cmHz1∕2∕W at 120K and a bias of −5V with a peak detection wavelength around 4.1μm and a quantum efficiency of 35%. Due to the low dark current and high responsivity, a clear photoresponse has been observed at room temperature, which gives a detectivity of 6.7×107cmHz1∕2∕W.
167 citations
TL;DR: In this paper, a metal-semiconductor-metal (MSM) photoconductive detector was fabricated on c-axis preferred oriented ZnO film prepared on quartz by radio frequency magnetron sputtering.
Abstract: In this study, metal–semiconductor–metal (MSM) photoconductive detector was fabricated on c -axis preferred oriented ZnO film prepared on quartz by radio frequency magnetron sputtering. With the applied bias below 3 V, the dark current was below 250 nA. The typical responsivity peaked at around 360 nm, and had values of 30 A/W. In addition, the UV (360 nm) to visible (450 nm) rejection ratio of around five orders could be extracted from the spectra response. Furthermore, the transient response measurement revealed fast photoresponse with a rise time of 20 ns.
165 citations
TL;DR: Use of the same GeSi composition and device structure allows efficient monolithic process integration of the modulators and the photodetectors on an SOI platform.
Abstract: We present a design of monolithically integrated GeSi electroabsorption modulators and photodetectors for electronic-photonic integrated circuits on a silicon-on-insulator (SOI) platform. The GeSi electroabsorption modulator is based on the Franz-Keldysh effect, and the GeSi composition is chosen for optimal performance around 1550 nm. The designed modulator device is butt-coupled to Si(core)/SiO(2)(cladding) high index contrast waveguides, and has a predicted 3 dB bandwidth of >50 GHz and an extinction ratio of 10 dB. The same device structure can also be used for a waveguide-coupled photodetector with a predicted responsivity of > 1 A/W and a 3 dB bandwidth of > 35 GHz. Use of the same GeSi composition and device structure allows efficient monolithic process integration of the modulators and the photodetectors on an SOI platform.
137 citations
TL;DR: In this article, the dependence of the quantum efficiency on device thickness of type-II InAs∕GaSb superlattice photodetectors with a cutoff wavelength around 12μm was reported.
Abstract: The authors report the dependence of the quantum efficiency on device thickness of type-II InAs∕GaSb superlattice photodetectors with a cutoff wavelength around 12μm. The quantum efficiency and responsivity show a clear delineation in comparison to the device thickness. An external single-pass quantum efficiency of 54% is obtained for a 12μm cutoff wavelength photodiodes with a π-region thickness of 6.0μm. The R0A value is kept stable for the range of structure thicknesses allowing for a specific detectivity (2.2×1011cmHz∕W).
01 Jan 2007
TL;DR: In this paper, the authors reported on the characterization of VDI's zerobias Schottky detectors and showed that under low power operation the detectors achieve a measured noise-equivalent power (NEP) of about 1.5x10 W/√Hz, even without signal modulation.
Abstract: Schottky barrier diodes can be used as direct detectors throughout the millimeterand submillimeterwave bands. When the diodes are optimized to have a low forward turn-on voltage, the detectors can achieve excellent frequency response and bandwidth, even with zero-bias. This paper reports on the characterization of VDI’s zerobias Schottky detectors. Responsivity typically ranges from 4,000 V/W at 100 GHz to 400 V/W at 900 GHz and each detector achieves good responsivity across the entire singlemoded bandwidth of the input rectangular waveguide. Under low power operation the detectors achieve a measured noise-equivalent-power (NEP) of about 1.5x10 W/√Hz, even without signal modulation. Such high sensitivity is expected for any zero-bias diode detector with high responsivity when there is no incident RF power; since only thermal noise can be generated under this condition. However, as the input power is increased, excess noise is generated. This noise typically has a 1/f power spectrum and is commonly known as flicker noise. Flicker noise becomes increasingly important as the input power is increased and signal modulation is generally required to achieve maximum sensitivity. The signal-to-noise of the VDI zero-bias detectors has been carefully measured as a function of input power and modulation rate. This data allows the user to understand the sensitivity of the detector under real operating conditions, and is therefore far more useful than the simple measurement of detector NEP with zero RF power, which is commonly quoted in the literature for new diode detector designs. Index Terms — Terahertz detectors, zero-bias detectors, noise-equivalent power, flicker noise.
TL;DR: The integrated device operates at 1550 nm with a responsivity of 5.7 A/W and a receiver sensitivity of -17.5 dBm at 2.5 Gb/s and is tapered to increase coupling efficiency and to minimize reflections.
Abstract: We report the integration of a hybrid silicon evanescent waveguide photodetector with a hybrid silicon evanescent optical amplifier. The device operates at 1550 nm with a responsivity of 5.7 A/W and a receiver sensitivity of -17.5 dBm at 2.5 Gb/s. The transition between the passive silicon waveguide and the hybrid waveguide of the amplifier is tapered to increase coupling efficiency and to minimize reflections.
TL;DR: In this article, a Schottky ultraviolet photodiode using a (0001) ZnO single crystal grown by the hydrothermal growth method is reported, which consisted of a semitransparent Pt film for the Schittky electrode and an Al thin film for Ohmic electrode.
Abstract: A Schottky ultraviolet photodiode using a (0001) ZnO single crystal grown by the hydrothermal growth method is reported. The photodiode consisted of a semitransparent Pt film for the Schottky electrode and an Al thin film for the Ohmic electrode. The photodiode had polarity dependences on current-voltage characteristics and on responsivity. In the case of the Schottky electrode on the zinc surface, the responsivity was 0.185A∕W at a wavelength of 365nm. On the other hand, the responsivity was 0.09A∕W for an oxygen surface. The results are attributed to the polarity dependences of surface chemical reactivity and the surface state density on ZnO surfaces.
TL;DR: In this paper, the InGaAs-InP modified charge compensated uni- traveling carrier photodiodes with both absorbing and nonabsorbing depleted region are demonstrated, and the fiber-coupled external quantum efficiency was 60% (responsivity at 1550 nm = 0.75 A/W).
Abstract: InGaAs-InP modified charge compensated uni- traveling carrier photodiodes with both absorbing and nonabsorbing depleted region are demonstrated. The fiber-coupled external quantum efficiency was 60% (responsivity at 1550 nm = 0.75 A/W). A 40-mum-diameter photodiode achieved 14-GHz bandwidth and 25-dBm RF output power and a 20-mum-diameter photodiode exhibited 30-GHz bandwidth and 15.5-dBm RF output power. The saturation current-bandwidth products are 1820 mA ldr GHz and 1560 mA GHz for the 40-mum-diameter and 40-mum-diameter devices, respectively.
TL;DR: Preliminary results for THz radiation show that glow discharge indicator lamps as room-temperature detectors yield good responsivity and noise-equivalent power.
Abstract: Glow discharge plasma, derived from direct-current gas breakdown, is investigated in order to realize an inexpensive terahertz (THz) room-temperature detector. Preliminary results for THz radiation show that glow discharge indicator lamps as room-temperature detectors yield good responsivity and noise-equivalent power. Development of a focal plane array (FPA) using such devices as detectors is advantageous since the cost of a glow discharge detector is approximately $0.2-$0.5 per lamp, and the FPA images will be diffraction limited. The detection mechanism of the glow discharge detector is found to be the enhanced diffusion current, which causes the glow discharge detector bias current to decrease when exposed to THz radiation.
TL;DR: In this article, self-assembled InAs-InGaAs-GaAs quantum dots are exploited for the development of large-format long-wavelength infrared focal plane arrays (FPAs).
Abstract: Epitaxially grown self-assembled InAs-InGaAs-GaAs quantum dots (QDs) are exploited for the development of large-format long-wavelength infrared focal plane arrays (FPAs). The dot-in-a-well (DWELL) structures were experimentally shown to absorb both 45deg and normal incident light, therefore, a reflection grating structure was used to enhance the quantum efficiency. The devices exhibit peak responsivity out to 8.1 mum, with peak detectivity reaching ~1times1010 Jones at 77 K. The devices were fabricated into the first long-wavelength 640times512 pixel QD infrared photodetector imaging FPA, which has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60-K operating temperature
TL;DR: In this article, a 320×256 middle-wavelength infrared focal plane array operating at temperatures up to 200K based on an InAs quantum dot/InGaAs quantum well/InAlAs barrier detector was reported.
Abstract: This letter reports a 320×256 middle-wavelength infrared focal plane array operating at temperatures up to 200K based on an InAs quantum dot/InGaAs quantum well/InAlAs barrier detector grown on InP substrate by low pressure metal organic chemical vapor deposition. The device’s low dark current density and the persistence of the photocurrent up to room temperature enabled the high temperature imaging. The focal plane array had a peak detection wavelength of 4μm, a responsivity of 34mA∕W, a conversion efficiency of 1.1%, and a noise equivalent temperature difference of 344mK at an operating temperature of 120K.
TL;DR: In this paper, the authors present measurement results of compact and efficient InAlAs-InGaAs metal-semiconductor-metal photodetectors integrated on silicon-on-insulator (SOI) waveguides.
Abstract: We present measurement results of compact and efficient InAlAs-InGaAs metal-semiconductor-metal photodetectors integrated on silicon-on-insulator (SOI) waveguides. These thin-film devices are heterogeneously integrated on the SOI substrate by means of low-temperature die-to-wafer bonding using divinyldisiloxane benzocyclobutene (DVS-BCB). The responsivity of a 30-mum-long detector is 1.0 A/W at a wavelength of 1550 nm and the dark current is 4.5 nA at a bias voltage of 5 V.
TL;DR: In this paper, the 4H-SiC p-i-n avalanche photodiodes (APDs) with very low dark current were reported, and the peak responsivity at unity gain is 93 mA/W (external quantum efficiency = 41%) at lambda = 280 nm.
Abstract: We report 4H-SiC p-i-n avalanche photodiodes (APDs) with very low dark current. When biased for a photocurrent gain M of 1000, a 100-mum-diameter device exhibits dark current of 5 pA (63 nA/cm2), corresponding to primary multiplied dark current of 5 fA (63 pA/cm2). The peak responsivity at unity gain is 93 mA/W (external quantum efficiency = 41%) at lambda = 280 nm. The excess noise factor corresponds to k = 0.1. Detection of several tens of femtowatts of ultraviolet light is reported.
TL;DR: In this article, the authors reported high performance solar-blind photodetectors with reproducible avalanche gain as high as 1560 under ultraviolet illumination, where the dark currents of the 40μm diameter devices were measured to be lower than 8fA for bias voltages up to 20V.
Abstract: The authors report high performance solar-blind photodetectors with reproducible avalanche gain as high as 1560 under ultraviolet illumination. The solar-blind photodetectors have a sharp cutoff around 276nm. The dark currents of the 40μm diameter devices are measured to be lower than 8fA for bias voltages up to 20V. The responsivity of the photodetectors is 0.13A∕W at 272nm under 20V reverse bias. The thermally limited detectivity is calculated as D*=1.4×1014cmHz1∕2W−1 for a 40μm diameter device.
01 Sep 2007
TL;DR: In this paper, zero-bias Schottky barrier diodes can be used as direct detectors throughout the millimeter and sub-millimeter wave bands, and they can achieve excellent frequency response and bandwidth, even with zero bias.
Abstract: Schottky barrier diodes can be used as direct detectors throughout the millimeter- and submillimeter- wave bands When the diodes are optimized to have a low forward turn-on voltage, the detectors can achieve excellent frequency response and bandwidth, even with zero-bias This paper reports on the characterization of VDI's zero- bias Schottky detectors Responsivity typically ranges from 4,000 V/W at 100 GHz to 400 V/W at 900 GHz and each detector achieves good responsivity across the entire single- moded bandwidth of the input rectangular waveguide Under low power operation the detectors achieve a measured noise-equivalent-power (NEP) of about 15 x 10-12 W/radicHz
TL;DR: In this article, a high-quality Ga-doped ZnO film was epitaxially grown on a Rplane sapphire substrate by plasma-assisted molecular-beam epitaxy.
Abstract: A high-quality Ga-doped ZnO film was epitaxially grown on a R-plane sapphire substrate by plasma-assisted molecular-beam epitaxy. Photoconductor devices with Al/Ti Ohmic contacts were fabricated. Photoluminescence and photocurrent measurements were carried out to study the emission and absorption properties of the Ga-doped ZnO film. Both spectra are consistent with each other showing good response in the ultraviolet region and weak response in the green–yellow band. Peak responsivity of 1.68 A/W at 20 V bias for 374 nm light was obtained in the ultraviolet region. Transient response of the device is slow due to the presence of the deep levels.
TL;DR: In this article, a red light sensor with pentacene phototransistors (PTs) with a thin film transistor (TFT) configuration was investigated as a red-light sensor.
Abstract: Pentacene phototransistors (PTs) prepared with a thin film transistor (TFT) configuration were investigated as a red light sensor. The pentacene TFTs showed an efficient photo-current response under various intensities of both modulated or continuous red light. The pentacene PTs showed a reliable high responsivity of 1 A/W and the ratio of photocurrent to dark current (IPh/IDark) was 9000 under visible light at a wavelength of 650 nm due to the relatively small band gap of pentacene. � 2007 Elsevier Ltd. All rights reserved.
TL;DR: In this paper, enhanced ultraviolet photoresponse was observed in rf magnetron sputtered ZnO thin films interfaced with ultrathin overlayers of different metals (Al, Cu, Sn, Pb, Au and Te).
Abstract: Enhanced ultraviolet (UV) photoresponse is observed in rf magnetron sputtered ZnO thin films interfaced with ultrathin overlayers of different metals (Al, Cu, Sn, Pb, Au, and Te). Electrons transferred from a metal layer to the semiconductor at the interface compensate the surface states and increase the dark conductivity. Depending on the number of injected electrons, surface states are compensated to different extents and correspondingly increase the photoconductivity. The photoresponse of the Sn∕ZnO bilayer sample exhibits the highest responsivity (∼6kV∕W) at low UV intensity of 140μW∕cm2 (λ=365nm) with a relatively fast response speed of 65ms.
TL;DR: In this article, the authors report on short-wavelength In0.53Ga0.47As∕AlAs0.56Sb0.44 quantum cascade detectors (QCDs).
Abstract: The authors report on short-wavelength In0.53Ga0.47As∕AlAs0.56Sb0.44 quantum cascade detectors (QCDs). At room temperature, one device detects at 505meV (2.46μm) with a responsivity of 2.57mA∕W, while a second QCD is sensitive at 580meV (2.14μm) with a responsivity of 0.32mA∕W.
TL;DR: In this article, the authors presented a 120 × 90 element thermoelectric infrared focal plane array with a precisely patterned Au-black absorber that provides high responsivity and a low cost potential.
Abstract: This paper presents a 120 × 90 element thermoelectric infrared focal plane array with a precisely patterned Au-black absorber that provides high responsivity and a low cost potential. The device has a responsivity of 3900 V/W. The overall chip size is 14.4 mm × 11.0 mm with a 12.0 mm × 9.0 mm imaging area. Each detector consists of two pairs of p–n polysilicon thermocouples and has external dimensions of 100 μm × 100 μm and internal electrical resistance of 90 kΩ. The precisely patterned Au-black infrared absorbing layer was achieved by both a low-pressure vapor deposition technique and a lift-off technique utilizing a PSG sacrificial layer. These techniques make it possible to obtain a Au-black pattern with the same degree of accuracy as with the CMOS process. The Au-black layer showed high absorptance of more than 90% to the light source with a wavelength of from 8 to 13 μm. This performance is suitable for automotive applications as well as consumer electronics.
TL;DR: In this paper, the authors demonstrate near-infrared waveguide photodetectors using Ge-SiGe quantum wells epitaxially grown on a silicon substrate, which exhibit a low dark current of 17.9 mA/cm2 at 5-V reverse bias.
Abstract: We demonstrate near-infrared waveguide photodetectors using Ge-SiGe quantum wells epitaxially grown on a silicon substrate. The diodes exhibit a low dark current of 17.9 mA/cm2 at 5-V reverse bias. The photodetectors are designed to work optimally at 1480 nm, where the external responsivity is 170 mA/W, which is mainly limited by the fiber-to-waveguide coupling loss. The 1480-nm wavelength matches the optimum wavelength for quantum-well electroabsorption modulators built on the same epitaxy, but these photodetectors also exhibit performance comparable to the demonstrated Ge-based detectors at longer wavelengths. At 1530 nm, we see open eye diagrams at 2.5-Gb/s operation and the external responsivity is as high as 66 mA/W. The technology is potentially integrable with the standard complementary metal-oxide-semiconductor process and offers an efficient solution for on-chip optical interconnects.
TL;DR: In this paper, a single-walled carbon nanotubes as absorber was used to construct a bolometer with an intrinsic electrical response at low frequency up to 109 V/W and noise equivalent power of 3×10−16 W/Hz1/2 at 4.2 K.
Abstract: A cryogenic bolometer has been fabricated using a bundle of single-walled carbon nanotubes as absorber. A bolometric response was observed when the device was exposed to radiation at 110 GHz. The temperature response was 0.4 mV/K, with an intrinsic electrical responsivity at low frequency up to 109 V/W and noise equivalent power of 3×10−16 W/Hz1/2 at 4.2 K. The response is largest at input power levels of a few femtowatts and decreases inversely proportional to the input power. Low frequency noise shows a 1/f dependence.
TL;DR: In this article, a metal-semiconductor-metal (MSM) ZnO photodiodes with palladium contact electrodes were fabricated with an incident wavelength of 370 nm and an applied bias of 1 V, and it was found that maximum responsivity of the Pd/ZnO/Pd MSM photodetectors was 0.051 A W � 1, which corresponds to a quantum efficiency of 11.4%.