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Showing papers on "Photodiode published in 2000"


Journal ArticleDOI
TL;DR: In this paper, the electrical and optical properties of photodiodes fabricated in GaN grown by metalorganic chemical vapor deposition have been investigated, and it is shown that small-area devices exhibit stable gain with no evidence of microplasmas.
Abstract: We report the electrical and optical characteristics of avalanche photodiodes fabricated in GaN grown by metalorganic chemical vapor deposition. The current–voltage characteristics indicate a multiplication of >25. Experiment indicates and simulation verifies that the magnitude of the electric field at the onset of avalanche gain is ⩾3 MV/cm. Small-area devices exhibit stable gain with no evidence of microplasmas.

727 citations


Journal ArticleDOI
TL;DR: In this paper, an InP-InGaAs uni-travelling-carrier photodiode with a 3 dB bandwidth of 310 GHz and a FWHM of 0.97ps was fabricated.
Abstract: The authors have fabricated an InP-InGaAs uni-travelling-carrier photodiode that exhibits a 3 dB bandwidth of 310 GHz and a pulse width (FWHM) of 0.97ps. Both of which are record values for photodetectors operating at a wavelength of 1.55 /spl mu/m. The average electron velocity in the depletion region is estimated to be 3.0/spl times/10/sup 7/ cm/s.

289 citations


Book ChapterDOI
TL;DR: In recent years significant progress has been achieved in the synthesis of various types of polymer-nanocomposites and in the understanding of the basic principles which determine their optical, electronic and magnetic properties.
Abstract: In recent years significant progress has been achieved in the synthesis of various types of polymer-nanocomposites and in the understanding of the basic principles which determine their optical, electronic and magnetic properties. As a result nanocomposite-based devices, such as light emitting diodes, photodiodes, photovoltaic solar cells and gas sensors, have been developed, often using chemically orientated synthetic methods such as soft lithography, lamination, spin-coating or solution casting.

282 citations


Patent
Subramanian Muthu1, Chin Chang1
27 Dec 2000
TL;DR: In this paper, the combined light output (chromaticity) of a white light emitting LED luminaire is automatically controlled based on measurements by a single photodiode arranged to measure the light outputs of at least a plurality of the LEDs in the array.
Abstract: The combined light output (chromaticity) of a white light emitting LED luminaire is electronically controlled based on measurements by a single photodiode arranged to measure the light outputs of at least a plurality of the LEDs in the array. This is accomplished by measuring the light output of the LEDs in each color separately in a sequence of time pulses. For an array of red, green, and blue LEDs there are three time pulses in a measuring sequence. During each time pulse, the current for the color being measured is turned off. The response time of a typical photodiode is extremely short, so the measuring sequence can be performed in a sufficiently short time that an-observer will not detect it (e.g. 10 ms). Measured light outputs for the colors are compared to desired outputs, which may be set by user controls, and changes to the power supply for the color blocks are made as necessary. Chromaticity is thus automatically controlled without regard to the factors which may cause it to change. The user inputs permit varying the desired chromaticity to either warm white (more red output) or cool white (more blue output).

277 citations


Journal ArticleDOI
TL;DR: In this paper, two new modifications of LGP have been designed and produced, each of them consists of 104 pixels 10×10 μm 2 size with area of 1 mm 2, these pixels operate as an independent photon counters, giving the output signal as a sum of the signals from pixels fired by photons.
Abstract: Recent results on Limited Geiger-mode Microcell Silicon Photodiode (LGP) are described. Two new modifications of LGP have been designed and produced. Each of them consists of 104 pixels 10×10 μm 2 size with area of 1 mm 2 . These pixels operate as an independent photon counters, giving the output signal as a sum of the signals from pixels fired by photons. The effective “gain” is large (≈105). The efficiency of the visible light photon detection of few percents has been measured. Low-temperature dark rate dependence has been studied. The timing by LGP at the level of 100 ps (FWHM) was found.

223 citations


Proceedings ArticleDOI
TL;DR: In this paper, the performance of narrow gap semiconductor photodiodes is investigated for short-wavelength IR, 1-3 $mUm; medium-length IR, 3-5 micrometers ; and long-length infrared, 8-14 micrometer ; the operating temperature for HgCdTe detectors is higher than for other types of photon detectors.
Abstract: At present efforts in IR detector research are directed towards improving the performance of single element devices and large electronically scanned arrays, and to obtain higher operating temperature of detectors. Another important aim is to make IR detectors cheaper and more convenient to use. Investigations of the performance of narrow gap semiconductor photodiodes are presented. Recent progress in different IR photodiode technologies is discussed: HgCdTe photodiodes, InSb photodiodes, alternative to HgCdTe III-V and II-VI ternary alloy photodiodes, and monolithic lead chalcogenide photodiodes. Investigations of the performance of photodiodes operated at short wavelength IR, 1-3 $mUm; medium wavelength IR, 3-5 micrometers ; and long wavelength IR, 8- 14 micrometers ; are presented. The operating temperature for HgCdTe detectors is higher than for other types of photon detectors. HgCdTe detectors with background limited performance operate with thermoelectric coolers in the medium wavelength range, instead the long wavelength detectors operate at approximately equals 100 K. HgCdTe is characterized by high absorption coefficient and quantum efficiency and relatively low thermal generation rate compared to other detectors.

204 citations


Journal Article
TL;DR: In this article, the operation, design, and performance of the uni-traveling-carrier photodiode (UTC-PD) is reviewed. But the authors do not consider the use of InP/InGaAs as an optoelectronic driver.
Abstract: This paper reviews the operation, design, and performance of the uni-traveling-carrier-photodiode (UTC-PD). The UTC-PD is a new type of photodiode that uses only electrons as its active carriers and its prime feature is high current operation. A small signal analysis predicts that a UTC-PD can respond to an optical signal as fast as or faster than a pin-PD. A comparison of measured pulse photoresponse data reveals how the saturation mechanisms of the UTC-PD and pin-PD differ. Applications of InP/InGaAs UTC-PDs as optoelectronic drivers are also presented. key words: photodiode, photoreceiver, InP, InGaAs

183 citations


Journal ArticleDOI
TL;DR: In this paper, a soft embossing technique for printing a submicrometer grati plate was used to increase the conversion efficiency of photovoltaic devices, as is cheap and simple technology.
Abstract: Increasing the conversion efficiency is very important in photovoltaic devices, as is cheap and simple technology. Here is demonstrated a soft embossing technique for printing a submicrometer grati ...

181 citations


Journal ArticleDOI
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


Journal ArticleDOI
TL;DR: The performance of selected, commercially available InGaAs/InP avalanche photodiodes operating in a photon-counting mode at an incident wavelength of 1.55 microm is described and a discussion on the optimum operating conditions and their relationship to the electric field distribution within the device is presented.
Abstract: The performance of selected, commercially available InGaAs/InP avalanche photodiodes operating in a photon-counting mode at an incident wavelength of 1.55 microm is described. A discussion on the optimum operating conditions and their relationship to the electric field distribution within the device is presented.

132 citations


Journal ArticleDOI
TL;DR: In this article, a new structure of Silicon Avalanche Detectors with high internal ampli"cation has been designed, manufactured and tested for registration of visible light photons and charge particles, and the main features of MetalResistor-Semiconductor (MRS) structures are the high charge multiplication in nonuniform electric field near the needle-aided junction and negative feedback for stabilization of avalanche process due to resistive layer.
Abstract: The development of a high quantum e$ciency, fast photodetector, with internal gain ampli"cation for the wavelength range 450}600 nm is one of the critical issues for experimental physics } registration of low-intensity light photons #ux. The new structure of Silicon Avalanche Detectors with high internal ampli"cation (105}106) has been designed, manufactured and tested for registration of visible light photons and charge particles. The main features of MetalResistor-Semiconductor (MRS) structures are the high charge multiplication in nonuniform electric "eld near the ‘needlea pn-junction and negative feedback for stabilization of avalanche process due to resistive layer. ( 2000 Elsevier Science B.V. All rights reserved.

Journal ArticleDOI
15 Oct 2000
TL;DR: In this paper, a monolithic active pixel sensor (MAPS) for charged particle tracking based on a novel detector structure was proposed, simulated, fabricated and tested, which is inseparable from the readout electronics, since both of them are integrated onto the same, standard for a CMOS process.
Abstract: A monolithic active pixel sensor (MAPS) for charged particle tracking based on a novel detector structure was proposed, simulated, fabricated and tested. The detector designed accordingly to this idea is inseparable from the readout electronics, since both of them are integrated onto the same, standard for a CMOS process, low-resistivity silicon wafer. The individual pixel is comprised of only 3 MOS transistors and a photodiode collecting the charge created in a thin undepleted epitaxial layer. This approach provides the whole detector surface sensitive to radiation (100% fill factor) with reduced pixel pitch(very high spatial resolution). This yields a low cost, high resolution and thin detecting device. The detailed device simulations using an ISE-TCAD package have been carried out in order to study a charge collection mechanism and to validate the proposed idea. Consequently, two prototype chips have been fabricated using 0.6 /spl mu/m and 0.35 /spl mu/m CMOS processes. Special radiation tolerant layout techniques were used in the second chip design. Both chips were tested and fully characterised. The pixel conversion gain was calibrated using 5.9 keV photons and prototype devices were exposed to the 120 GeV/c pion beams at CERN. Obtained results preceded by general design ideas and simulation results are reviewed.

Journal ArticleDOI
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.

Journal ArticleDOI
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...

Journal ArticleDOI
TL;DR: In this article, a transparent Schottky-barrier ultraviolet detector on GaN layers over sapphire substrates was presented. Butler et al. used SiO2 surface passivation to reduce the reverse leakage currents to a value as low as 1 pA at 5 V reverse bias for 200 μm diameter device.
Abstract: We report on a transparent Schottky-barrier ultraviolet detector on GaN layers over sapphire substrates. Using SiO2 surface passivation, reverse leakage currents were reduced to a value as low as 1 pA at 5 V reverse bias for 200 μm diameter device. The device exhibits a high internal gain, about 50, at low forward biases. The response time (about 15 ns) is RC limited, even in the internal gain regime. A record low level of the noise spectral density, 5×10−23 A2/Hz, was measured at 10 Hz. We attribute this low noise level to the reduced reverse leakage current.

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this article, the growth, fabrication, and characterization of AlxGa1−xN (0⩽x⩾0.60) heteroepitaxial back-illuminated solar-blind p-i-n photodiodes on (0001) sapphire substrates were reported.
Abstract: We report the growth, fabrication, and characterization of AlxGa1−xN (0⩽x⩽0.60) heteroepitaxial back-illuminated solar-blind p-i-n photodiodes on (0001) sapphire substrates. The group III-nitride heteroepitaxial layers are grown by low-pressure metalorganic chemical vapor deposition on double polished sapphire substrates using various growth conditions. The back-illuminated devices exhibit very low dark current densities. Furthermore, they exhibit external quantum efficiencies up to 35% at the peak of the photoresponse (λ∼280 nm). Improvements were made to the growth technique in order to achieve crack-free Al0.4Ga0.6N active regions on a thick Al0.6Ga0.4N window layer and to obtain activated p-type Al0.4Ga0.6N layers.

Journal ArticleDOI
TL;DR: The contribution of the Cerenkov radiation to the light seen by the photodiode has been modelled and the model predictions have been tested using bremsstrahlung beams of peak energy between 13 and 20 MV, showing agreement with measurement.
Abstract: An organic scintillator detector system has been developed for radiotherapy bremsstrahlung dosimetry. The scintillators are connected to photodiodes by light pipes as the photodiodes must be removed and shielded from the incident radiation. The photodiodes see visible and near-visible light emissions from the scintillator as well as Cerenkov and fluorescence radiation that has been generated and trapped in the scintillator and light pipe. The Cerenkov and fluorescence radiation limits the accuracy of the dosimeter. This work examines a range of methods for diminishing the signal contribution of Cerenkov and fluorescence radiation while optimizing the scintillator signal. Three methods of achieving these goals have been used. They are: reflective coatings on the scintillator, long-wavelength-emitting scintillators used in conjunction with the photodiode, and absorptive filters placed between the light guide and photodiode. The contribution of the Cerenkov radiation to the light seen by the photodiode has been modelled and the model predictions have been tested using bremsstrahlung beams of peak energy between 13 and 20 MV, showing agreement with measurement.

Patent
28 Nov 2000
TL;DR: In this paper, a three-dimensional imaging system is fabricated on a single IC using CMOS fabrication techniques, which includes a two-dimensional array of pixel light sensing detectors and dedicated electronics and associated processing circuitry.
Abstract: A three-dimensional imaging system is fabricated on a single IC. The system includes a two-dimensional array of pixel light sensing detectors and dedicated electronics and associated processing circuitry, all preferably fabricated on a single IC using CMOS fabrication techniques. The system includes a detector array comprising a plurality of pixel photodiodes and photodiode circuits, wherein each pixel photodiode acquires delay time data and pulse brightness data simultaneously. The system emits an energy pulse at time t0 and a fraction of the energy is returned to the array by a target object. Photodiodes in the array output a brightness signal B(t) that is integrated. An elapsed time ET from t0 to when said B(t) attains a predetermined threshold value is determined, where the slope of B(t) is B/PW, where B is B(t) after integrating over a time equal to the emitted pulse width PW. Time-of-flight TOF representing time from t0 to when a photodiode begins to detect energy is determined, where TOF=ET−IT, where IT is proportional to PW/B. A system processor determines distance from the system to the target object, from TOF and the velocity of light, and can translate TOF into commands to control electronic devices.

Journal ArticleDOI
TL;DR: In this paper, the mean energy required for producing an electron-hole pair, W, is determined from the spectral responsivity of photodiodes using spectrally dispersed synchrotron radiation.
Abstract: Ionizing radiation can be detected by the measurement of the charge carriers produced in a detector. The improved semiconductor technology now allows detectors operating near the physical limits of the detector materials to be designed. The mean energy required for producing an electron–hole pair, W, is a material property of the semiconductor. Here, the determination of W from the spectral responsivity of photodiodes is demonstrated. Using spectrally dispersed synchrotron radiation, different types of semiconductor photodiodes have been examined in the UV-, VUV-, and soft X-ray spectral range. Their spectral responsivity was determined with relative uncertainties between 0.4% and 1% using a cryogenic electrical-substitution radiometer as primary detector standard. Results are presented for silicon n-on-p junction photodiodes and for GaAsP/Au Schottky diodes at room temperature. The investigations for silicon covered the complete spectral range from 3 to 1500 eV, yielding a constant value W=(3.66±0.03) eV for photon energies above 50 eV, a maximum value of W=4.4 eV at photon energies around 6 eV, and a linear relation W=hν (one electron per photon) for photon energies below 4 eV. For GaAsP, we obtained a constant value of W=4.58 eV in the photon energy range from 150 to 1500 eV, with a relative uncertainty of 1–3%, depending on the photon energy.

Journal ArticleDOI
TL;DR: In this paper, the reverse characteristics of the Schottky contact were examined by taking into account the barrier height dependence on the electric field and tunneling through the barrier, and it was shown that the logarithmic dependence of the reverse current on the reverse bias is a linear function.
Abstract: The electrical behavior of metal–semiconductor–metal (MSM) Schottky barrier photodiode structures is analyzed by means of current–voltage measurements at different temperatures. The reverse characteristics of the Schottky contact are examined by taking into account the barrier height dependence on the electric field and tunneling through the barrier. It is shown that, under these conditions, the logarithmic dependence of the reverse current on the reverse bias is a linear function and allows us to evaluate the barrier height, saturation current density, and junction ideality factor of the MSM-photodiode Schottky contact. The results are well consistent with experiment.

Journal ArticleDOI
TL;DR: In this paper, two concepts have been implemented: intermediate conversion of X-rays to light by a scintillator, detected by an array of light sensitive pixels, comprising a photodiode and a switching device, either a TFT or a diode.
Abstract: The replacement of the radiographic film in medical imaging has been the driving force in X-ray imaging developments. It requires a ∼40 cm wide detector to cover all examinations, an equivalent noise level of 1–5 X-ray quanta per pixel, and spatial resolution in the range 100–150 μm. The need for entirely electronic imaging equipments has fostered the development of many X-ray detectors, most of them based on an array of amorphous silicon pixels, which is the only technology capable to achieve such large areas. Essentially, two concepts have been implemented: • intermediate conversion of X-rays to light by a scintillator, detected by an array of light sensitive pixels, comprising a photodiode and a switching device, either a TFT or a diode. • conversion into electron–hole pairs in a photoconductor, collected by an array of electrodes and switches. In both cases, charge amplifiers read the generated charges line by line. Scintillator and photoconductor-based systems are now close to production. They achieve better image quality than the classic film-screen combination, at lower X-ray dose and with a much broader dynamic range. Dynamic imaging up to 30 frames/s has been demonstrated. The technical challenges at the level of the a-Si array are the number of acceptable defects, the on/off ratio of the switches, the quantum efficiency of the photodiodes, the memory effects associated with traps in a-Si. Of course, long-term reliability is a major concern for medical components.

Journal ArticleDOI
TL;DR: In this article, a fixed-pattern-noise (FPN)-reduction technology consisting of a five-transistor pixel circuit, a hole accumulation diode for sensing elements, and a correlated-double-sampling (CDS) circuit with an I-V converter in an output stage circuit, is applied to a 1/3-inch 640/spl times/480-pixel CMOS image sensor.
Abstract: A simple fixed-pattern-noise (FPN)-reduction technology, which consists of a five-transistor pixel circuit, a hole accumulation diode for sensing elements, and a correlated-double-sampling (CDS) circuit with an I-V converter in an output stage circuit, is applied to a 1/3-inch 640/spl times/480-pixel CMOS image sensor. The five-transistor pixel circuit outputs the current mode pixel signal with a reset level and a signal level successively in one pixel period. The I-V converter is designed to reduce a signal-line voltage to close to the ground level in order to give sufficient voltage to an amplification transistor in a pixel. The CDS circuit receives a pixel signal from the I-V converter and performs as an FPN-reduction circuit by subtracting a signal level from a reset level of a pixel signal. Owing to the technology, the CMOS image sensor achieved a sensitivity of 0.52 V/lx/spl middot/s, a saturation signal of 200 mV, a dynamic range of 61 dB and a dark current of 150 pA/cm/sup 2/.

Journal ArticleDOI
10 Dec 2000
TL;DR: In this paper, a high-photosensitivity and no-crosstalk pixel technology has been developed for an embedded active-pixel CMOS image sensor, by using a 0.35-/spl mu/m CMOS logic process.
Abstract: A high-photosensitivity and no-crosstalk pixel technology has been developed for an embedded active-pixel CMOS image sensor, by using a 0.35-/spl mu/m CMOS logic process. To increase the photosensitivity, we developed a deep p-well photodiode and an antireflective film, consisting of Si/sub 3/N/sub 4/ film, for the photodiode surface. To eliminate the high voltage required for the reset transistor in the pixel, we used a depletion-type transistor as the reset transistor. The reset transistor also operates as an overflow control gate, which enables antiblooming overflow when excess charge is generated in the photodiode by high-illumination conditions. To suppress pixel crosstalk caused by obliquely incident light, a double-metal photoshield was used, while crosstalk caused by electron diffusion in the substrate was suppressed by using the deep p-well photodiode. A 1/3-in 330-k-pixel active-pixel CMOS image sensor was fabricated using this technology. A sensitivity improvement of 110% for 550-nm incident light was obtained by using the deep p-well photodiode, while an improvement of 24% was obtained by using the antireflective film. The pixel crosstalk was suppressed to less than 1% throughout the range of visible light.

Journal ArticleDOI
TL;DR: In this article, the third-order intermodulation distortions of a high frequency, large optical cavity p-i-n waveguide photodiode were characterized up to 18 GHz using a two-tone measurement.
Abstract: In Hayes's (1993) and Williams's (1996) analyses, the photodiode nonlinearity is attributed to the space charge screening effect. In this paper, the third-order intermodulation distortions of a high frequency, large optical cavity p-i-n waveguide photodiode are characterized up to 18 GHz using a two-tone measurement. At high bias voltage, the third-order intercept point (IP3) of the waveguide photodiode is constant at low frequency and /spl sim/f/sup -3/ at high frequency. This closely agrees with our model, which is based upon variation of the photodiode impedance. The measured IP3 of the same device at low bias voltages indicates the contribution of space charge screening under low bias voltage or severe saturation.

Patent
24 Nov 2000
TL;DR: In this article, a photoelectric conversion device consisting of an avalanche photodiode 12 and a voltage applying circuit 15 which applies a voltage to it, with a voltage control circuit 18 for controlling the applied voltage provided as well.
Abstract: PROBLEM TO BE SOLVED: To provide a photoelectric conversion device wherein the fact that the multiplication factor of avalanche phenomenon depends on the electric field intensity is utilized for variable sensitivity. SOLUTION: A photoelectric conversion device comprises an avalanche photodiode 12 and a voltage applying circuit 15 which applies a voltage to it, for variable applied voltage, with a voltage control circuit 18 for controlling the applied voltage provided as well. The voltage control circuit 18 judges the quantity of received light by monitoring the output of the photodiode. When the quantity of received light is large, the multiplication factor is taken as 1 where the value of applied voltage causes no avalanche phenomenon, while, when the quantity of received light is small, the multiplication factor is taken as 1 or more where the value of applied voltage causes an avalanche phenomenon.

01 Jan 2000
TL;DR: This thesis describes position-sensitive devices (PSDs) and optical sensor systems suitable for industrial tracking and displacement sensing applications and proposes a method based on averaging the positions of multiple reflectors in order to improve the precision in turbulence-limited cases.
Abstract: This thesis describes position-sensitive devices (PSDs) and optical sensor systems suitable for industrial tracking and displacement sensing applications. The main application areas of the proposed sensors include automatic pointing of a rangefinder beam and measuring the lateral displacement of an object. A conventional tracking sensor is composed of a laser illuminator, a misfocused quadrant detector (QD) receiver and a corner cube retroreflector (CCR) attached to the target. The angular displacement of a target from the receiver optical axis is detected by illuminating the target and determining the direction of the reflection using the QD receiver. The main contribution of the thesis is related to the modifications proposed for this conventional construction in order to make its performance sufficient for industrial applications that require a few millimetre to submillimetre accuracy. The work includes sensor optical construction modifications and the designing of new types of PSDs. The conventional QD-based sensor, although electrically very sensitive, is not considered optimal for industrial applications since its precision is severely hampered by atmospheric turbulence due to the misfocusing needed for its operation. Replacing the CCR with a sheet reflector is found to improve the precision of the conventional sensor construction in outdoor beam pointing applications, and is estimated to allow subcentimetre precision over distances of up to 100 m under most operating conditions. Submillimetre accuracy is achievable in close-range beam pointing applications using a small piece of sheet reflector, coaxial illumination and a focused QD receiver. Polarisation filtering is found to be effective in eliminating the main error contributor in close-range applications, which is low reflector background contrast, especially in cases when a sheet reflector has a specularly reflecting background. The tracking sensor construction is also proposed for measuring the aiming trajectory of a firearm in an outdoor environment. This time an order of magnitude improvement in precision is achieved by replacing the QD with a focused lateral effect photodiode (LEP). Use of this construction in cases of intermediate atmospheric turbulence allows a precision better than 1 cm to be achieved up to a distance of 300 m. A method based on averaging the positions of multiple reflectors is also proposed in order to improve the precision in turbulence-limited cases. Finally, various types of custom-designed PSDs utilising a photodetector array structure are presented for long-range displacement sensing applications. The goal was to be able to replace the noisy LEP with a low-noise PSD without compromising the low turbulence sensitivity achievable with the LEP. An order of magnitude improvement in incremental sensitivity is achievable with the proposed

Patent
01 Mar 2000
TL;DR: In this paper, a fully depleted photodiode accumulates charge into a separate floating diffusion, which has less capacitance than the overall photodiodes, resulting in a knee-shaped transfer characteristic for charge accumulation that results in a larger dynamic range.
Abstract: A fully depleted photodiode (200) accumulates charge into both the photodiode (200) and a separate floating diffusion (205). The photodiode (200) is a buried photodiode having two PN junctions for photocarrier conversion. The floating diffusion (205) has less capacitance than the overall photodiode, thereby resulting in a knee-shaped transfer characteristic for charge accumulation that results in a larger dynamic range. The floating diffusion (205) is connected to an output transistor (210). A reset transistor has a gate (206) that is activated to connect the floating diffusion (205) to a diffusion region (208) that is held at VDD to reset the photodiode (200).

Journal ArticleDOI
TL;DR: In this article, the authors investigated the avalanche multiplication and excess noise properties of a range of submicron Si diodes and found that the excess noise was below that predicted by conventional local noise theory.
Abstract: The avalanche multiplication and excess noise properties of a range of submicron Si diodes have been investigated. In these thin diodes the excess noise is found to fall below that predicted by conventional local noise theory. Modeling of the multiplication and excess noise using a recurrence method, which includes the dead space for carrier ionization, gives good agreement with experiment. This suggests that the dead space can reduce the excess noise in submicron Si diodes.

Journal ArticleDOI
TL;DR: In this paper, the authors present some examples of novel devices based on p-n junction heterostructures operating in the long wavelength, middle wavelength and short wavelength spectral ranges.