Showing papers on "Photodiode published in 2005"

Visible and near-infrared responsivity of femtosecond-laser microstructured silicon photodiodes.

Abstract: We investigated the current-voltage characteristics and responsivity of photodiodes fabricated with silicon that was microstructured by use of femtosecond-laser pulses in a sulfur-containing atmosphere. The photodiodes that we fabricated have a broad spectral response ranging from the visible to the near infrared (400-1600 nm). The responsivity depends on substrate doping, microstructuring fluence, and annealing temperature. We obtained room-temperature responsivities as high as 100 A/W at 1064 nm, 2 orders of magnitude higher than for standard silicon photodiodes. For wavelengths below the bandgap we obtained responsivities as high as 50 mA/W at 1330 nm and 35 mA/W at 1550 nm.

Ge-on-Si vertical incidence photodiodes with 39-GHz bandwidth

Abstract: Vertical-incidence Germanium photodiodes grown on thin strain-relaxed buffers on Silicon substrates are reported. For a mesa-type detector with a diameter of 10 /spl mu/m, a resistance-capacitance-limited 3-dB bandwidth of 25.1 GHz at an incident wavelength of 1552 nm and zero external bias has been measured. At a reverse bias of 2 V, the bandwidth is 38.9 GHz. The detector comprises a 300-nm-thick intrinsic region, and thus, has the potential for easy integration with Si circuitry and exhibits zero bias external quantum efficiencies of 23%, 16%, and 2.8% at 850, 1298, and 1552 nm, respectively.

Solid state image pickup device and camera

Abstract: A solid state image pickup device which can prevent color mixture by using a layout of a capacitor region provided separately from a floating diffusion region and a camera using such a device are provided. A photodiode region is a rectangular region including a photodiode. A capacitor region includes a carrier holding unit and is arranged on one side of the rectangle of the photodiode region as a region having a side longer than the one side. In a MOS unit region, an output unit region including an output unit having a side longer than the other side which crosses the one side of the rectangle of the photodiode region is arranged on the other side. A gate region and the FD region are arranged between the photodiode region and the capacitor region.

Underwater optical communications systems. Part 2: basic design considerations

Abstract: Acoustic systems may provide suitable underwater communications because sound propagates well in water. However, the maximum data transmission rates of these systems in shallow littoral waters are ~10 kilobits per second (kbps) which may be achieved only at ranges of less than 100 m. Although underwater (u/w) wireless optical communications systems can have even shorter ranges due to greater attenuation of light propagating through water, they may provide higher bandwidth (up to several hundred kbps) communications as well as covertness. To exploit these potential advantages, we consider the basic design issues for u/w optical communications systems in this paper. In addition to the basic physics of u/w optical communications with environmental noise, we consider system performance with some state-of-the-art commercial off-the-shelf (COTS) components, which have promise for placing u/w optical communications systems in a small package with low power consumption and weight. We discuss light sources which show promise for u/w optical transmitters such as laser diodes (LDs) and light emitting diodes (LEDs). Laser diodes with their output frequency shifted into the 500- to 650-nm range can emit more energy per pulse than LEDs but are more expensive. Currently, LEDs emit substantial amounts of light and are typically very inexpensive. Also, COTS photodiodes can be used as detectors which can respond to pulses several nanoseconds wide. Transmitter broadcast angles and detector fields of view (FOVs) with pointing considerations are discussed. If the transmitter broadcast angle and the detector FOV are both narrow, the signal-to-noise ratio (SNR) of the received pulse is higher but the pointing accuracy of transmitter and receiver is critical. If, however, the transmitter broadcast angle and/or the detector FOV is wide, pointing is less critical but SNR is lower and some covertness may be lost. The propagation of the transmitted light in various clear oceanic and turbid coastal water types is considered with range estimates for some COTS light sources and detectors. We also consider the effects of environmental noise such as background solar radiation, which typically limits performance of these systems

Continuous THz-wave generation using antenna-integrated uni-travelling-carrier photodiodes

Abstract: Photonic generation of continuous millimetre- and sub-millimetre waves up to the THz range using antenna-integrated uni-travelling-carrier photodiodes is described. A device integrating a wideband log-periodic antenna exhibits a maximum output power of 2.6 ?W at 1.04 THz with good linearity. A module with a quasi-optical output port fabricated for practical use generates almost the same output power as the chip at around 1 THz and operates at frequencies of up to 1.5 THz. The output power level and the operation frequency are records for wideband photodiodes operating at 1.55 ?m. Devices integrating resonant narrowband dipole antennae have also been fabricated and the output power increases at resonant peak frequencies confirmed. The device having a peak at 1.04 THz exhibits a maximum (detected) output power of 10.9??W at 1.04 THz with good linearity. This output power is the highest value ever directly generated from a photodiode in the THz range, and several times higher than the maximum value reported by the low-temperature-grown GaAs photoconductive switch at around 1 THz.

ZnO devices: Photodiodes and p-type field-effect transistors

Abstract: The potential use of ZnO-based photonic and electronic devices has been demonstrated by the fabrication of prototype ultraviolet (UV) photodetector and field-effect transistor (FET) devices that contain films of p-type ZnO with arsenic as the p-type dopant. These p-type films have high crystalline quality and show long-term stability. The ZnO UV photodetectors are based on p-n junctions. The FETs are made with metal-semiconductor Schottky contacts on p-type ZnO and are normally off (enhancement) devices. The spectral and electrical characteristics of these devices are presented and explained.

Thin-film organic photodiodes as integrated detectors for microscale chemiluminescence assays

Abstract: We report the use of thin-film organic photodiodes as integrated optical detectors for microscale chemiluminescence. The copper phthalocyanine–fullerene (CuPc–C 60 ) small molecule photodiodes have an external quantum efficiency of ∼30% at 600–700 nm, an active area of 2 mm × 8 mm and a total thickness of ∼2 mm. Simple detector fabrication, based on layer-by-layer vacuum deposition, allows facile integration with planar chip-based systems. To demonstrate the efficacy of the approach, CuPc–C 60 photodiodes were used to monitor a peroxyoxalate based chemiluminescence reaction (PO-CL) within a poly(dimethylsiloxane) (PDMS) microfluidic device. Optimum results were obtained for applied reagent flow rates of 25 μL/min, yielding a CL signal of 8.8 nA within 11 min. Reproducibility was excellent with typical relative standard deviations (R.S.D.) below 1.5%. Preliminary quantitation of hydrogen peroxide yielded a detection limit of ∼1 mM and linearity over at least three decades. With improved sensitivity and when combined with enzymatic assays the described integrated devices could find many applications in point-of-care diagnostics.

Photonic generation of continuous THz wave using uni-traveling-carrier photodiode

Abstract: A uni-traveling-carrier photodiode (UTC-PD) is monolithically integrated with a wideband log-periodic toothed antenna for generating millimeter and submillimeter waves at frequencies of up to terahertz range. A module with a quasi-optical output port fabricated for practical use operates up to 1.5 THz and generates an output power of 2.3 /spl mu/W at 1.04 THz with good linearity. The output power level and the operation frequency are records for wideband PD modules operating at 1.55 /spl mu/m. An investigation of the operational characteristics of the UTC-PD reveals that the effective use of the electron-velocity overshoot in the junction depletion layer is important for maximizing the output power in the terahertz range.

Optical characteristics of one-dimensional Si∕SiO2 photonic crystals for thermophotovoltaic applications

Abstract: This article presents a detailed exploration of the optical characteristics of various one-dimensional photonic crystal structures designed for use as a means of improving the efficiency and power density of thermophotovoltaic (TPV) devices. The crystals being investigated have a ten-layer quarter-wave periodic structure, and are based on Si∕SiO2 and Si∕SiON material systems. For TPV applications the crystals are designed to act as filters, transmitting photons with wavelengths below 1.78μm to a GaSb photodiode, while reflecting photons of longer wavelengths back to the source of thermal radiation. In the case of the Si∕SiO2 structure, the Si and SiO2 layers were designed to be 170 and 390nm thick, respectively. This structure was fabricated using low-pressure chemical vapor deposition. Reflectance and transmittance measurements of the fabricated Si∕SiO2 photonic crystals were taken from 0.8to3.3μm for both polarizations and for a range of incident angles. Measurement results were found to correlate well ...

Optical transmitting apparatus, optical receiving apparatus, and optical communication system comprising them

Abstract: A phase shift unit provides a prescribed phase difference (π/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal f 0 is superimposed on one of the optical signals. A signal of which phase is shifted by π/2 from the low-frequency signal f 0 is superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2f 0 component contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2f 0 component becomes the minimum.

Uncooled operation of type-II InAs∕GaSb superlattice photodiodes in the midwavelength infrared range

Abstract: We report high performance uncooled midwavelength infrared photodiodes based on interface-engineered InAs∕GaSb superlattice. Two distinct superlattices were designed with a cutoff wavelength around 5μm for room temperature and 77 K. The device quantum efficiency reached more than 25% with responsivity around 1A∕W. Detectivity was measured around 109cmHz1∕2∕W at room temperature and 1.5×1013cmHz1∕2∕W at 77 K under zero bias. The devices were without antireflective coating. The device quantum efficiency stays at nearly the same level within this temperature range. Additionally, Wannier–Stark oscillations in the Zener tunneling current were observed up to room temperature.

A 100 dB dynamic range CMOS image sensor using a lateral overflow integration capacitor

Abstract: The wide DR CMOS image sensor incorporates a lateral overflow capacitor in each pixel to integrate the overflow charges from the photodiode when it saturates. The 7.5/spl times/7.5 /spl mu/m/sup 2/ pixel, 1/3" VGA sensor fabricated in a 0.35 /spl mu/m 3M2P CMOS process achieves a 100 dB dynamic range with no image lag, 0.15 mV/sub rms/ random noise and 0.15 mV fixed pattern noise.

Passivation of InAs∕(GaIn)Sb short-period superlattice photodiodes with 10μm cutoff wavelength by epitaxial overgrowth with AlxGa1−xAsySb1−y

Abstract: An approach for the passivation of photodiodes based on compounds of the InAs∕GaSb∕AlSb materials family is presented. The passivation is realized by the overgrowth of patterned mesa devices with a quaternary AlxGa1−xAsySb1−y layer, lattice matched to the GaSb substrate. Proof of concept is demonstrated on infrared photodiodes based on InAs∕(GaIn)Sb superlattices with 10μm cutoff wavelength operating at 77 K where suppression of surface leakage currents is observed.

A 3-Gb/s optical detector in standard CMOS for 850-nm optical communication

Abstract: This paper presents a monolithic optical detector, consisting of an integrated photodiode and a preamplifier in a standard 0.18-/spl mu/m CMOS technology. A data rate of 3 Gb/s at BER <10/sup -11/ was achieved for /spl lambda/=850 nm with 25-/spl mu/W peak-peak optical power. This data rate is more than four times than that of current state-of-the-art optical detectors in standard CMOS reported so far. High-speed operation is achieved without reducing circuit responsivity by using an inherently robust analog equalizer that compensates (in gain and phase) for the photodiode roll-off over more than three decades. The presented solution is applicable to various photodiode structures, wavelengths, and CMOS generations.

Thermoreflectance based thermal microscope

Abstract: Thermal images of active semiconductor devices are acquired and processed in real time using visible light thermoreflectance imaging with 34mK sensitivity. By using a 16×16 alternating current coupled photodiode array with synchronous frequency domain filtering a dynamic range of 123dB is achieved for 1s averaging. Thus with a stable and higher power light source, fundamentally the camera can reach 6mK sensitivity over a submicron area. The number of pixels in the image is increased to 160×160 by multiple frame image enhancement and submicron spatial resolution is achieved. The photodiode array system has a maximum 40kHz frame rate and generates a synchronous trigger for recovery of the phase signal. Amplitude and phase images of the thermoreflectance signal for 50×50 micron square active SiGe based microcoolers are presented.

A frequency multiplexed near-infrared topography system for imaging functional activation in the brain

Abstract: We have developed a novel near-infrared optical topography system that can acquire images of functional activation in the human brain at 10 frames per second using 32 detectors. The image acquisition rate is inversely proportional to the number of detectors, so the maximum acquisition rate using four detectors is 80Hz. 16 laser diode sources (8 at 785 and 8 at 850nm) are illuminated simultaneously, and each of 8 avalanche photodiode detectors records light from several sources at the same time. The contribution from each source is demultiplexed in software using fast Fourier transforms. This allows for a more flexible, smaller, and less complex system than is achievable using traditional hardware demodulation techniques, such as lock-in amplifiers. The system will eventually incorporate a total of 64 sources and 32 detectors, enabling the entire adult cortex to be imaged. The system is designed to be as flexible as possible, and to be applicable to a wide variety of experimental and clinical needs. To thi...

Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam

Abstract: A temperature insensitive fiber Bragg grating (FBG) liquid level sensor based on bending cantilever beam (BCB) is proposed and demonstrated. The BCB induces axial strain gradient along the sensing FBG, resulting in a Bragg bandwidth modulation. The broadening of FBG spectrum bandwidth and the reflection optical power change with the liquid level and they are insensitive to spatially uniform temperature variations. For a liquid level variation of 500 mm and a temperature range from 0/spl deg/C to 80/spl deg/C, the measured liquid level fluctuates less than 2% without any temperature compensation. By optical power detection via a pin photodiode, the liquid-level sensor avoids complex demodulation process and potentially costs low.

A digital pixel sensor array with programmable dynamic range

Abstract: This paper presents a digital pixel sensor (DPS) array employing a time domain analogue-to-digital conversion (ADC) technique featuring adaptive dynamic range and programmable pixel response The digital pixel comprises a photodiode, a voltage comparator, and an 8-bit static memory The conversion characteristics of the ADC are determined by an array-based digital control circuit, which linearizes the pixel response, and sets the conversion range The ADC response is adapted to different lighting conditions by setting a single clock frequency Dynamic range compression was also experimentally demonstrated This clearly shows the potential of the proposed technique in overcoming the limited dynamic range typically imposed by the number of bits in a DPS A 64 /spl times/ 64 pixel array prototype was manufactured in a 035-/spl mu/m, five-metal, single poly, CMOS process Measurement results indicate a 100 dB dynamic range, a 41-s mean dark time and an average current of 16 /spl mu/A per DPS

Solid-state imagine device, line sensor, optical sensor, and method for operating solid-state imaging device

Abstract: A solid-state imaging device having a widened dynamic range while maintaining a high sensitivity and a high S/N ratio, a line sensor, an optical sensor, and a method for operating a solid-state imaging device adopted so as to widen the dynamic range of the solid-state imaging device while maintaining a high sensitivity and a high S/N ratio are disclosed. The solid-state imaging device is composed of an array of integrated pixels each of which comprises a photodiode (PD) for generating optical charges on receiving light, a transfer transistor (Tr1) for transferring the optical charges, and a storage capacitive element (Cs) connected to the photodiode (PD) at least through the transfer transistor (Tr1) and serving to store the optical charges overflowing from the photodiode (PD) at least through the transfer transistor (Tr1) during storage operation.

Avalanche multiplication in AlGaN based solar-blind photodetectors

Abstract: Avalanche multiplication has been observed in solar-blind AlGaN-based p-i-n photodiodes. Upon ultraviolet illumination, the optical gain shows a soft breakdown starting at relatively low electric fields, eventually saturating without showing a Geiger mode breakdown. The devices achieve a maximum optical gain of 700 at a reverse bias of 60 V. By modeling the device, it is found that this corresponds to an electric-field strength of 1.7MV∕cm.

SiCGe/SiC heterojunction and its MEDICI simulation of optoelectronic characteristics

Abstract: Optoelectronic characteristics of the SiC1−xGex /SiC heterojunction photodiode are simulated using MEDICI after the theoretical investigation of key properties for SiC1−xGex. The calculations show that SiC1−xGex /SiC with x=0.3 may have a small lattice mismatch with 3C-SiC and a good response to the visible light and the near infrared light. The response spectrum of the SiC1−xGex /SiC heterojunction photodiode, which consists of a p-type SiC1−xGex absorption layer with a doping concentration of 1×1015cm−3, a thickness of 1.6μm and x=0.3, has a peak of 250mA/W at 0.52μm and the peak can even reach 102mA/W at 0.7μm.

Thermally stable visible-blind diamond photodiode using tungsten carbide Schottky contact

Abstract: We have developed a thermally stable, deep-ultraviolet (DUV) photodiode using tungsten carbide (WC) Schottky and Ti/WC ohmic contacts for a boron-doped homoepitaxial p-diamond epilayer. Effects of thermal annealing in an argon ambient on the electrical and photoresponse properties were investigated. Annealing at temperatures up to 550°C improves the rectifying current-voltage characteristics, resulting in a dramatic enhancement of DUV responsivity at 220nm by a factor of 4×103. A blind ratio as large as 105 between DUV and visible light has been achieved at a reverse bias as small as 1V. Development of the thermally stable WC-based Schottky and ohmic contacts provides a route for stable operation of a diamond photodetector at high temperatures.

Measuring the absolute light yield of scintillators

Abstract: The absolute light yield of four different scintillation materials measured with two photomultiplier tubes and two avalanche photodiodes is presented. Commonly, the photoelectron yields and electron–hole pair yields are corrected for the quantum efficiency of the detector, as specified by the manufacturer, to obtain the absolute photon yield. However, the effective quantum efficiency under scintillation measurement conditions is substantially higher due to back reflection. Only when back reflection is properly accounted for, the absolute photon yields obtained with the photomultipliers agree with those obtained with the photodiodes. The effect of optical coupling between the scintillator and detector is also discussed.

High-speed, high-responsivity, and high-power performance of near-ballistic uni-traveling-carrier photodiode at 1.55-/spl mu/m wavelength

Abstract: In this letter, we demonstrate a novel photodiode at a 1.55-/spl mu/m wavelength: the near-ballistic uni-traveling-carrier photodiode (UTC-PD). After a p/sup +/ delta-doped layer was inserted into the collector of a UTC-PD, near-ballistic transport of photogenerated electrons under high reverse bias voltage (-5 V) and a high output photocurrent (/spl sim/30 mA) was observed. The demonstrated device has been combined with an evanescently coupled optical waveguide to attain high responsivity and high saturation power performance. Extremely high responsivity (1.14 A/W), a high electrical bandwidth (around 40 GHz), and a high saturation current-bandwidth product (over 1280 mA/spl middot/GHz, at 40 GHz) with high saturation radio-frequency power (over 12 dBm at 40 GHz) have been achieved simultaneously at a 1.55-/spl mu/m wavelength.

A high-sensitivity CMOS image sensor with gain-adaptive column amplifiers

Abstract: A high-sensitivity CMOS image sensor using gain-adaptive column amplifiers is presented and tested. The use of high gain for the column amplifier reduces input-referred random noise, and when coupled with a column-based digital noise cancellation technique, also reduces fixed pattern noise. An experimental application of the circuit using 0.25-/spl mu/m CMOS technology with pinned photodiodes gave an rms random noise of 263 /spl mu/V and an rms fixed pattern noise of 50 /spl mu/V.

Organic photodiodes on newspaper

Abstract: Organic semiconductors have ob-tained considerable interest in the fields of electronic and photonic devices due to a wide range of applications as low-cost, large-area and disposable or throwaway electron-ics on thin and flexible substrates. In particular organic photodiodes have improved to a level which is sufficient for many applications [1–7]. In the present paper we demonstrate a major advantage of organic semiconductor devices over their inorganic counterparts – namely the possibility to manufacture or-ganic devices on almost arbitrary user defined substrates. For this purpose we fabricated organic photodiodes on conventional newspaper (“Die Zeit”). Newspaper is a high volume substrate, which is widely used in daily life, revealing special properties like flexibility and low cost [8, 9]. On the other hand newspaper is a quite complicated substrate for electronic devices. Compared to other sub-strate types newspaper exhibits poor mechanical and chemical stability and furthermore it shows a very rough surface. The demonstration of fully functional devices on newspaper has potentially important technological implica-tions as it opens the way to fabricate organic optoelectronic devices on nearly every kind of substrate. Imaginable ap-plications include for example wearable textile electronics or the field of ubiquitous computing, where optimized or-ganic solar cells would provide the power and autonomy. The fabricated organic photodiodes resemble the well approved classical Tang-type [1] pn-heterojunction device consisting of p-type conducting copper phthalocyanine (CuPc) and n-type perylene tetracarboxylic bisbenzimida-zole (PTCBI). Tang-type photodiodes show a good stabil-ity at ambient conditions and exhibit large photocurrents of the order of mA/cm

CMOS image sensor and method for manufacturing the same

Abstract: A CMOS image sensor and a method for manufacturing the same improve light-receiving efficiency and maintain a margin in the design of a metal line. The CMOS image sensor includes a transparent substrate including an active area having a photodiode region and a transistor region and a field area for isolation of the active area, a p-type semiconductor layer on the transparent substrate, a photodiode in the p-type semiconductor layer corresponding to the photodiodes region, and a plurality of transistors in the p-type semiconductor layer corresponding to the transistor region.

On the performance and surface passivation of type II InAs∕GaSb superlattice photodiodes for the very-long-wavelength infrared

Abstract: We demonstrate very-long-wavelength infrared type II InAs∕GaSb superlattice photodiodes with a cutoff wavelength (λc,50%) of 17μm. We observed a zero-bias, peak Johnson noise-limited detectivity of 7.63×109cmHz1∕2∕W at 77 K with a 90%–10% cutoff width of 17 meV, and quantum efficiency of 30%. Variable area diode zero-bias resistance-area product (R0A) measurements indicated that silicon dioxide passivation increased surface resistivity by nearly a factor of 5, over unpassivated photodiodes, and increased overall R0A uniformity. The bulk R0A at 77 K was found to be 0.08Ωcm2, with RA increasing more than twofold at 25 mV reverse bias.

CMOS image sensor

Abstract: A complementary metal-oxide semiconductor (CMOS) image sensor comprises a photodiode region generating electrical charges in response to incident light thereon. The CMOS image sensor further comprises a first floating diffusion layer adapted to receive the electrical charges from the photodiode region in response to a global transfer signal and a second floating diffusion region adapted to receive the electrical charges from the first floating diffusion region in response to a pixel selection signal.