Showing papers on "Photodiode published in 2006"

nBn detector, an infrared detector with reduced dark current and higher operating temperature

Abstract: This letter presents a type of infrared detector named the nBn detector. The nBn design essentially eliminates Shockley-Read-Hall generation currents. The result is greatly reduced dark current and noise, compared to other midwave infrared detectors, such as p-n photodiodes. This enables the nBn to operate at background-limited infrared photodetection conditions at significantly higher temperatures than conventional midwave infrared detectors and have greater detectivity near room temperature. The nBn is demonstrated in InAs and InAsSb materials, exhibiting cutoff wavelengths of 3.4 and 4.2μm, respectively.

Production of photocurrent due to intermediate-to-conduction-band transitions : A demonstration of a key operating principle of the intermediate-band solar cell

Abstract: We present intermediate-band solar cells manufactured using quantum dot technology that show for the first time the production of photocurrent when two sub-band-gap energy photons are absorbed simultaneously. One photon produces an optical transition from the intermediate-band to the conduction band while the second pumps an electron from the valence band to the intermediate-band. The detection of this two-photon absorption process is essential to verify the principles of operation of the intermediate-band solar cell. The phenomenon is the cornerstone physical principle that ultimately allows the production of photocurrent in a solar cell by below band gap photon absorption, without degradation of its output voltage.

Microstructured silicon photodetector

Abstract: Photodetectors fabricated on microstructured silicon are reported. The photodetectors exhibited high photoresponse; at 3V bias, the responsivities were 92A∕W at 850nm and 119A∕W at 960nm. At wavelengths longer than 1.1μm, the photodetectors still showed strong photoresponse. A generation-recombination gain mechanism has been proposed to explain the photoresponse of these photodiodes. From measurements of the noise current density, the calculated gain was approximately 1200 at 3V bias.

Terabus: Terabit/Second-Class Card-Level Optical Interconnect Technologies

Abstract: In the "Terabus" optical interconnect program, optical data bus technologies are developed that will support terabit/second chip-to-chip data transfers over organic cards within high-performance servers, switch routers, and other intensive computing systems. A complete technology set is developed for this purpose, based on a chip-like optoelectronic packaging structure (Optochip), assembled directly onto an organic card (Optocard). Vertical-cavity surface emitting laser (VCSEL) and photodiode arrays (4times12) are flip-chip bonded to the driver and receiver IC arrays implemented in 0.13-mum CMOS. The IC arrays are in turn flip-chip assembled onto a 1.2-cm2 silicon carrier interposer to complete the transmitter and receiver Optochips. The organic Optocard incorporates 48 parallel multimode optical waveguides on a 62.5-mum pitch. A simple scheme for optical coupling between the Optochip and the Optocard is developed, based on a single-lens array etched onto the backside of the optoelectronic arrays and on 45deg mirrors in the waveguides. Transmitter and receiver operation is demonstrated up to 20 and 14 Gb/s per channel, respectively. The power dissipation of 10-Gb/s single-channel links over multimode fiber is as low as 50 mW

Fabrication and characterization of ZnO nanowires based UV photodiodes

Abstract: A heterojunction of n-type zinc oxide (ZnO) nanowires and p-type silicon has been successfully constructed to demonstrate ultraviolet (UV) photodiodes. The prototype device consists of naturally doped n-type ZnO nanowires grown on top of a (1 0 0) p-silicon substrate by the bottom-up growth process. The diameter of the nanowires is in the range of 70–120 nm, and the length is controlled by the growth time. The isolation is achieved by using spin-on glass (SOG) that also works as the foundation of the top electrode. The current–voltage (I–V) characteristics show the typical rectifying behavior of heterojunctions, and the photodiode exhibits response of ∼0.07 A/W for UV light (365 nm) under a 20 V reverse bias.

Lab-on-a-chip with integrated optical transducers

Abstract: Taking the next step from individual functional components to higher integrated devices, we present a feasibility study of a lab-on-a-chip system with five different components monolithically integrated on one substrate. These five components represent three main domains of microchip technology: optics, fluidics and electronics. In particular, this device includes an on-chip optically pumped liquid dye laser, waveguides and fluidic channels with passive diffusive mixers, all defined in one layer of SU-8 polymer, as well as embedded photodiodes in the silicon substrate. The dye laser emits light at 576 nm, which is directly coupled into five waveguides that bring the light to five different locations along a fluidic channel for absorbance measurements. The transmitted portion of the light is collected at the other side of this cuvette, again by waveguides, and finally detected by the photodiodes. Electrical read-out is accomplished by integrated metal connectors. To our knowledge, this is the first time that integration of all these components has been demonstrated.

Wireless power beaming to common electronic devices

Abstract: A method and apparatus for wireless power beaming consisting of a transmitter assembly ( 20 ), free space ( 40 ), and an optical-to-electric assembly ( 50 ). The transmitter assembly ( 20 ) has eye-safe lasers ( 26 ) that create a beam of light ( 90 ). The beam of light goes through free space ( 40 ) and impinges upon the surface of optical-to-electric assembly ( 50 ). Optical-to-electric assembly ( 50 ) has power conversion photodiode(s) ( 54 ) to convert the energy in the light ( 90 ) into electricity. Power Accounting ( 14 ) accounts for the power in the beam and controls the lasers to turn them off whenever radiation is not accounted for in the system.

Digital silicon photomultiplier for TOF-PET

Abstract: A radiation detector includes an array of detector pixels each including an array of detector cells. Each detector cell includes a photodiode biased in a breakdown region and digital circuitry coupled with the photodiode and configured to output a first digital value in a quiescent state and a second digital value responsive to photon detection by the photodiode. Digital triggering circuitry is configured to output a trigger signal indicative of a start of an integration time period responsive to a selected number of one or more of the detector cells transitioning from the first digital value to the second digital value. Readout digital circuitry accumulates a count of a number of transitions of detector cells of the array of detector cells from the first digital state to the second digital state over the integration time period.

Graded band gap for dark-current suppression in long-wave infrared W-structured type-II superlattice photodiodes

Abstract: A new W-structured type-II superlattice photodiode design, with graded band gap in the depletion region, is shown to strongly suppress dark currents due to tunneling and generation-recombination processes. The long-wave infrared (LWIR) devices display 19%–29% quantum efficiency and substantially reduced dark currents. The median dynamic impedance-area product of 216Ωcm2 for 33 devices with 10.5μm cutoff at 78K is comparable to that for state-of-the-art HgCdTe-based photodiodes. The sidewall resistivity of ≈70kΩcm for untreated mesas is also considerably higher than previous reports for passivated or unpassivated type-II LWIR photodiodes, apparently indicating self-passivation by the graded band gap.

Image sensor with microcrystalline germanium photodiode layer

Abstract: A microcrystalline germanium image sensor array. The array includes a number of pixel circuits fabricated in or on a substrate. Each pixel circuit comprises a charge collecting electrode for collecting electrical charges and a readout means for reading out the charges collected by the charge collecting electrode. A photodiode layer of charge generating material located above the pixel circuits convert electromagnetic radiation into electrical charges. This photodiode layer includes microcrystalline germanium and defines at least an n-layer, and i-layer and a p-layer. The sensor array also includes and a surface electrode in the form of a grid or thin transparent layer located above the layer of charge generating material. The sensor is especially useful for imaging in visible and near infrared spectral regions of the electromagnetic spectrum and provides imaging with starlight illumination.

Method and arrangement for measuring the distance to an object

Abstract: Arrangement ( 10 ) for measuring the distance to an object, comprising: a photonic source for illuminating said object using a continuous modulated photonic wave, a solid-state image sensor, comprising an array of avalanche photodiodes and a plurality of circuits for processing signals output by said avalanche photodiodes to yield data depending on the photonic wave reflected by said object onto said photodiodes. The circuit may comprise a multiplexer at the pixel level arranged so as to accumulate the signal output by the avalanche photodiode during different sub-periods in different storage devices.

The HgCdTe electron avalanche photodiode

Abstract: Electron injection avalanche photodiodes in short-wave infrared (SWIR) to long-wave infrared (LWIR) HgCdTe show gain and excess noise properties indicative of a single ionizing carrier gain process. The result is an electron avalanche photodiode (EAPD) with “ideal” APD characteristics including near noiseless gain. This paper reports results obtained on long-, mid-, and short-wave cutoff infrared Hg1−xCdxTe EAPDs (10 µm, 5 µm, and 2.2 µm) that use a cylindrical “p-around-n” front side illuminated n+/n-/p geometry that favors electron injection into the gain region. These devices are characterized by a uniform, exponential, gain voltage characteristic that is consistent with a hole-to-electron ionization coefficient ratio, k=αh/αe, of zero. Gains of greater than 1,000 have been measured in MWIR EAPDS without any sign of avalanche breakdown. Excess noise measurements on midwave infrared (MWIR) and SWIR EAPDs show a gain independent excess noise factor at high gains that has a limiting value less than 2. At 77 K, 4.3-µm cutoff devices show excess noise factors of close to unity out to gains of 1,000. A noise equivalent input of 7.5 photons at a 10-ns pulsed signal gain of 964 measured on an MWIR APD at 77 K provides an indication of the capability of this new device. The excess noise factor at room temperature on SWIR EAPDs, while still consistent with the k=0 operation, approaches a gain independent limiting value of just under 2 because of electron-phonon interactions expected at room temperature. The k=0 operation is explained by the band structure of the HgCdTe. Monte Carlo modeling based on the band structure and scattering models for HgCdTe predict the measured gain and excess noise behavior.

Design and performance of an InGaAs-InP single-photon avalanche diode detector

Abstract: This paper describes the design, fabrication, and performance of planar-geometry InGaAs-InP devices which were specifically developed for single-photon detection at a wavelength of 1550 nm. General performance issues such as dark count rate, single-photon detection efficiency, afterpulsing, and jitter are described.

W-structured type-II superlattice long-wave infrared photodiodes with high quantum efficiency

Abstract: Results are presented for an enhanced type-II W-structured superlattice (WSL) photodiode with an 11.3μm cutoff and 34% external quantum efficiency (at 8.6μm) operating at 80K. The new WSL design employs quaternary Al0.4Ga0.49In0.11Sb barrier layers to improve collection efficiency by increasing minority-carrier mobility. By fitting the quantum efficiencies of a series of p-i-n WSL photodiodes with background-doped i-region thicknesses varying from 1to4μm, the authors determine that the minority-carrier electron diffusion length is 3.5μm. The structures were grown on semitransparent n-GaSb substrates that contributed a 35%–55% gain in quantum efficiency from multiple internal reflections.

Image sensor having curved micro-mirrors over the sensing photodiode and method for fabricating

Abstract: The invention involves the integration of curved micro-mirrors over a photodiode active area (collection area) in a CMOS image sensor (CIS) process. The curved micro-mirrors reflect light that has passed through the collection area back into the photo diode. The curved micro-mirrors are best implemented in a backside illuminated device (BSI).

High bandwidth Ge p-i-n photodetector integrated on Si

Abstract: The authors present a germanium on silicon p-i-n photodiode for vertical light incidence. For a Ge p-i-n photodetector with a radius of 5μm a 3dB bandwidth of 25GHz is measured at an incident wavelength of 1.55μm and zero external bias. For a modest reverse bias of 2V, the 3dB bandwidth increases to 39GHz. The monolithically integrated devices are grown on Si with solid source molecular beam epitaxy. The complete detector structure consisting of a highly p-doped Ge buried layer, an intrinsic absorption region, and a highly n-doped top contact layer of Ge∕Si is grown in one continuous epitaxial run. A low growth temperature sequence was needed to obtain abrupt doping transitions between the highly doped regions surrounding the intrinsic layer. A theoretical consideration of the 3dB bandwidth of the Ge detector was used to optimize the layer structure. For a photodiode with 5μm mesa radius the maximum theoretical 3dB frequency is 62GHz with an intrinsic region thickness of 307nm.

Design Considerations for 1.06- $mu$ m InGaAsP–InP Geiger-Mode Avalanche Photodiodes

Abstract: For Geiger-mode avalanche photodiodes, the two most important performance metrics for most applications are dark count rate (DCR) and photon detection efficiency (PDE). In 1.06-mum separate-absorber-avalanche (multiplier) InP-based devices, the primary sources of dark counts are tunneling through defect levels in the InP avalanche region and thermal generation in the InGaAsP absorber region. PDE is the probability that a photon will be absorbed (quantum efficiency) times the probability that the electron-hole pair generated will actually cause an avalanche. A device model based on experimental data that can simultaneously predict DCR and PDE as a function of overbias and temperature is presented. This model has been found useful in predicting changes in performance as various device parameters, such as avalanche layer thickness, are modified. This has led to designs that are capable simultaneously of low DCR and high PDE

A sensitivity and linearity improvement of a 100-dB dynamic range CMOS image sensor using a lateral overflow integration capacitor

Abstract: In a CMOS image sensor featuring a lateral overflow integration capacitor in a pixel, which integrates the overflowed charges from a fully depleted photodiode during the same exposure, the sensitivity in nonsaturated signal and the linearity in saturated overflow signal have been improved by introducing a new pixel circuit and its operation. The floating diffusion capacitance of the CMOS image sensor is as small as that of a four transistors type CMOS image sensor because the lateral overflow integration capacitor is located next to the reset switch. A 1/3-inch VGA format (640/sup H//spl times/480/sup V/ pixels), 7.5/spl times/7.5 /spl mu/m/sup 2/ pixel color CMOS image sensor fabricated through 0.35-/spl mu/m two-poly three-metal CMOS process results in a 100 dB dynamic range characteristic, with improved sensitivity and linearity.

Temperature Measurements Using a Microoptical Sensor Based on Whispering Gallery Modes

Abstract: Temperature measurements were made using a novel microoptical sensor based on dielectric microspheres that are excited by coupling light from optical fibers. The technique exploits the morphology-dependent shifts in resonant frequencies that are commonly referred to as the whispering gallery modes. A change in the temperature of the microsphere leads to a change in both the size and the index of refraction of the sphere which results in a shift of the resonant frequency. By monitoring this shift, the temperature of the environment surrounding the sphere can be determined. The whispering gallery mode shifts are observed by scanning a tunable diode laser that is coupled into the optical fiber on one end and monitoring the transmission spectrum by a photodiode on the other. When the microsphere is in contact with a bare section of the fiber, the optical modes are observed as dips in the intensity of the light transmitted through the fiber. Temperature measurements were made in both air and water using this novel technique. Measurements by the microoptical sensor were compared to those by thermocouples with good agreement between the two sets of results.

GaN ultraviolet avalanche photodiodes with optical gain greater than 1000 grown on GaN substrates by metal-organic chemical vapor deposition

Abstract: We report the performance of GaN p-i-n ultraviolet avalanche photodiodes grown on bulk GaN substrates by metal-organic chemical vapor deposition The low dislocation density in the devices enables low reverse-bias dark currents prior to avalanche breakdown for ∼30μm diameter mesa photodetectors The photoresponse is relatively independent of the bias voltage prior to the onset of avalanche gain which occurs at an electric field of ∼28MV∕cm The magnitude of the reverse-bias breakdown voltage shows a positive temperature coefficient of ∼005V∕K, confirming that the avalanche breakdown mechanism dominates With ultraviolet illumination at λ∼360nm, devices with mesa diameters of ∼50μm achieve stable maximum optical gains greater than 1000 To the best of our knowledge, this is the highest optical gain achieved for GaN-based avalanche photodiodes and the largest area III-N avalance photodetectors yet reported

Solid state imaging device and its manufacturing method

Abstract: PROBLEM TO BE SOLVED: To provide a solid state imaging device which can improve an incident efficiency of light in a photoelectric transferring section, and its manufacturing method. SOLUTION: A CMOS image sensor 1 comprises: a semiconductor substrate 2; an N type impurity region 9, formed within the semiconductor substrate 2, where signal charge generated by the photoelectric transfer of photodiode 10 formed in a surface portion of the semiconductor substrate 2 is accumulated; a charge accumulating region 13 formed within the semiconductor substrate 2 and beneath the N type impurity region 9; a gate electrode 7, for transferring the signal charge accumulated in the N type impurity region 9 to the charge accumulating region 13, which is formed so that it may penetrate the semiconductor substrate 2; and a signal processing section 20, formed in a rear side of the semiconductor substrate 3, to which the signal charge transferred to the charge accumulating region 13 is inputted. COPYRIGHT: (C)2007,JPO&INPIT

Calibration of sampling oscilloscopes with high-speed photodiodes

Abstract: We calibrate the magnitude and phase response of equivalent-time sampling oscilloscopes to 110 GHz. We use a photodiode that has been calibrated with our electrooptic sampling system as a reference input pulse source to the sampling oscilloscope. We account for the impedance of the oscilloscope and the reference photodiode and correct for electrical reflections and distortions due to impedance mismatch. We also correct for time-base imperfections such as drift, time-base distortion, and jitter. We have performed a rigorous uncertainty analysis, which includes a Monte Carlo simulation of time-domain error sources combined with error sources from the deconvolution of the photodiode pulse, from the mismatch correction, and from the jitter correction

Imaging device and digital camera

Abstract: An imaging device includes an image sensor chip and a package for containing the image sensor chip. Formed in the package is a vent hole that is connected to an air pump. In a light receiving area of the image sensor chip, there are photodiodes and microlenses above them. The microlenses are made of a gel-like transparent material. When the internal air pressure of the package is changed by the air pump, each microlens transforms in response to the change of the internal air pressure, and thereby changes the surface curvature thereof.

Pinned photodiode structure and method of formation

Abstract: An imager having a photodiode with a shallow doping profile with respect to the top surface of a substrate is disclosed. An imager with a graded pinned surface layer, self-aligned to a gate stack is provided. A photodiode with a shallow doping profile with respect to the top surface of a substrate and a graded pinned surface layer, self-aligned to a gate stack is provided. These photodiodes exhibit reduced image lag, transfer gate leakage, and photodiode dark current generation.

ZnO tetrapod Schottky photodiodes

Abstract: The fabrication of an ultraviolet photodiode employing a single ZnO tetrapod nanocrystal is reported. This diode structure is prepared by depositing W and Pt electrodes to form Ohmic and Schottky contacts, respectively. Dark current-voltage measurements show rectifying behavior. The properties of the metal-semiconductor interface are studied with above and below band gap illumination. It is found that with increasing UV excitation the device converts from a rectifying to an Ohmic behavior. This effect is attributed to a flattening of the energy bands due to the migration of photogenerated carriers within the space charge region at the metal-semiconductor interface.

Image pickup device and camera with expanded dynamic range

Abstract: The image pickup device of the invention has a path deeper in a semiconductor substrate, than a region wherein a channel is formed, upon turning on a first MOS transistor, under a gate thereof. The path is arranged by forming a P-type layer for forming a potential barrier, within a P-type well excluding a region below the gate of the first MOS transistor. Thus, even when the first transfer MOS transistor is securely turned off at accumulation, carriers overflowing from a photodiode can flow into the path, thereby enabling to accumulate the carriers, overflowing from the photodiode, in a carrier accumulation region. Such structure allows to suppress a dark current generation from an interface of a gate oxide film of the first transfer MOS transistor, and also to expand the dynamic range of the image pickup device by the carriers overflowing from the photodiode and flowing through the path into the carrier accumulation region.

First results of scintillator readout with silicon photomultiplier

Abstract: A new type of silicon device has been realized that has many properties comparable to, or better than, a conventional PMT (Photomultiplier Tube). This paper presents the first results of using these photodetectors in place of a PMT in the readout of scintillators for possible PET (Positron Emission Tomography) applications. This device, the Silicon Photomultiplier (SiPM), is effectively an avalanche photodiode operated in Geiger mode. In Geiger-mode detectors, a very large current signal is produced regardless of the size of the input, giving just logical rather than proportional information. However, the SiPM is subdivided into a large number (1440) of microcells that act as independent and virtually identical Geiger-mode photodiodes. The outputs of all these individual microcells are connected so that the total output signal is the sum of the signals from all of the microcells that were activated. In this way proportional information can be obtained. As a consequence of their design, these detectors have potentially very fast timing, high gain (105-106) at low bias voltage (~50 V), a high quantum efficiency (35% at 500 nm), excellent single photoelectron resolution and are cheap to manufacture. Here we present results obtained with this new photodetector when used with pulsed LED and scintillator pixels

Ge on Si p-i-n photodiodes operating at 10 Gbit/s

Abstract: We report on fast p-i-n photodetectors operating in the near infrared and realized in pure germanium on silicon. The diodes were fabricated by chemical vapor deposition at 600°C without affecting the crystal quality and allowing the integration with standard silicon processes. We demonstrate responsivities of 0.4 and 0.2A∕W at 1.3 and 1.55μm, respectively, as well as operation at 10Gbit∕s.

CMOS image sensor and method for manufacturing the same

Abstract: A CMOS image sensor and a method for manufacturing the same, capable of preventing an interface between an active region and a field region in the CMOS image sensor from being damaged by ion implantation. The method comprises implanting dopant ions into a source region between a gate electrode of the reset transistor and the photodiode, using an ion implantation mask that covers predetermined locations of the field region and the source region.