A monolithic 1 × 10 array of silicon avalanche photodiodes

A monolithic 1 × 10 array of silicon avalanche photodiodes (Si-APD's) was fabricated. The deviations of breakdown voltages and current gains from mean values in an array were less than ±0.3 and ±2 percent, respectively. The optical interelemental coupling between the adjacent two elements in an array was estimated to be -57 dB.     

Flip-chip planar GaInAs/InP p-i-n photodiode array for paralleloptical transmission

A back-illuminated planar GaInAs/InP p-i-n photodiode array with a simple fabrication process was developed for application to parallel optical transmission. Four p-i-n photodiodes were integrated in the array. The average capacitance and dark current were as low as 0.12 pF and 8 pA, respectively, at -5 V. At a 1.55-μm wavelength, the quantum efficiency of each photodiode was over 80%. The cutoff frequency was 8-10 GHz with four photodiodes when the bias voltage was -3 V and the load resistance was 50 Ω. Crosstalk between channels was -12 dB at the cutoff frequency and -45 dB at 1 GHz     

A high speed tapped CCD photodiode linear image sensor

A tapped charge-coupled photodiode (CCPD) array for high speed document scanning applications has been developed. This linear sensor array is comprised of 1024 photodiode elements divided into 8 sections of 128 elements each and accessed by 16 CCD analog shift registers. This arrangement allows the device to operate at a maximum output data rate of 160 MHz. Utilizing diffused photodiodes for photosensing and CCD registers for low-noise signal extraction, this device has a dynamic range of 1000:1 and spectral response from .2 µm to 1.1 µm. The modular design also permits arrays of 512 or 256 elements.     

基于ZnO纳米线阵列和P3HT的混合光电二极管特性

为了发展低成本、大面积和高性能光电二极管,采用简单的化学浴沉积方法,在氧化铟锡(I TO) 玻璃基底上生长良好取向的ZnO纳米线阵列(ZNWA),然后在生长的ZNWA上旋涂规整的聚3-己 基噻吩(P3HT)层,形成结构为ITO/ZNWA/P3HT/Ag的光电二极管。系统研究了此光电二极管在 暗态和在太阳模拟器的光照下的电流-电压 (I-V)特性。实验结果表明,器件在暗态和光照下都表现出良好 的二极管特性。暗态下,在偏压±2V处的整流 率为3211, 理想因子为1.8、低开启电压为0.5V和反偏饱和电流为1．13×10－7 A。在20mW/cm²光照下,在偏压±2V处的整流率为39.1、开启电压为0.3V。器件中产生了大量的光生载流子,根据器件的能级结构图和光生载流子的 输运过程对此光电二极管的光响应机理进行了解释。     

High-speed Ga0.47In0.53As/InP infra-redSchottky-barrier photodiodes

The authors report a new high-speed InP-based Ga_1-xIn _xAs infra-red Schottky-barrier photodiode. The photodiodes were fabricated on both p- and n-GaInAs epilayers using Schottky barrier height enhancement technology. The response speed was measured by the impulse response and autocorrelation method; the risetimes of 85 ps for p-GaInAs and 180 ps for n-GaInAs photodiodes were obtained, which correspond to the 3 dB cutoff frequency of 2-4 GHz. The intrinsic response speed was 12 GHz for n-GaInAs and 18 GHz for p-GaInAs photodiodes based on SPICE simulation with measured device parameters. The photodiodes had the responsivity as high as 0.55 A/W and the quantum efficiency of up to 45% at 1.3-1.6 μm without antireflection coating     

A shallow flat p-well structure for interline-transfer CCD image sensors

This paper describes a newly-developed image-sensing element having a shallow flat p-well (SFPW) structure, and further mentions its application to a 490 × 510- and a 580 × 500-element device for use in the ⅔-in optical format. The structure consists of a shallow flat p-well in the imaging area that incorporates not only photodiodes for blooming suppression but also CCD shift registers for reduction of smearing. Desirable features such as 1) high resolution, 2) high aperture ratio, and 3) low smearing level were facilitated simultaneously by a combination of the SFPW structure with a transfer gate-less (TGL) and clock-line-isolated photodiode (CLIP) structure. Here, the conventional n⁺-p photodiode is replaced by an n⁺-n^--p structure, in which the n^-region serves as an overflow duct to the substrate for excess charge generated by optical overloads. It also contributes to maintaining the sensitivity at medium wavelengths. Either of these two image sensors have horizontal resolution in excess of 370 TV lines, an aperture ratio of over 32 percent, and a smearing level of less than -70 dB.     

The GaAlAsSb quaternary and GaAlSb ternary alloys and their application to infrared detectors

GaAlAsSb quaternary alloys and GaAlSb ternary alloys have been grown by liquid phase epitaxy (LPE) at 550°C and 450°C, respectively. The material compositions and epitaxial structures are suitable for fabricating photodiodes sensitive in the1.0-1.8 mum wavelength range. Various avalanche photodiode structures fabricated in these materials are discussed. The ion implanted GaAlAsSb APD's exhibit a high gain of 100, 82 percent quantum efficiency, and a FWHM of 400 ps. The heterojunction GaAlAsSb APD's have a gain of 40, 92 percent quantum efficiency, and a FWTM of 150 ps. The only remaining material problem which limits the performance of these devices is the high-surface leakage current.     

Planar embedded InP/GaInAs p-i-n photodiode for very high-speed operation

Planar embedded InP/GaInAs p-i-n photodiodes have been fabricated by using preferential ion-beam etching for planarizing and embedding the p-i-n photodiode structure in a semi-insulating InP substrate. The stray capacitances caused by a bonding pad and an interconnection have been markedly reduced, which resulted in extremely low capacitance of less than 0.08 pF for a diameter of 20 μm of photosensitive area. It has been demonstrated by an optical heterodyne technique that the photodiode exhibits a maximum cutoff frequency of 14 GHz. This result was analyzed taking the depletion layer thickness into account and has been found to be dominated by the carrier transit time. The demonstrated low capacitance and high-speed response result indicates the suitability of the p-i-n photodiodes not only for a discrete p-i-n photodiode but also for optoelectronic integration.     

Correlation of laser-beam-induced current with current-voltage measurements in HgCdTe photodiodes

Laser-beam-induced current (LBIC) is being investigated as an alternative to electrical measurements of individual photodiodes in a two-dimensional array. This is possible because LBIC only requires two electrical contacts to an array and the two-dimensional scanning of a focused laser beam across the array to image the entire array. The measured LBIC profiles, obtained from linear arrays of HgCdTe photodiodes, will be used to study the uniformity of photodiodes in the array and to extract the R₀A of the photodiodes. It will be shown that the shape of the LBIC signal is correlated to the electrical performance of the photodiode, with R₀A related to the spreading length of the photodiodes. Linear arrays of n-on-p, mid-wavelength infrared (MWIR) and long wave-length infrared (LWIR) devices were formed in liquid-phase epitaxy HgCdTe epilayers using a plasma junction-formation technique. The LBIC profiles were measured on each of the devices at various temperatures. For the MWIR devices, the extracted spreading length shows no correlation with R₀A. However, the LBIC signal does detect nonuniform devices within the array. For the case of the LWIR devices, the spreading length is extracted as a function of temperature, with the R₀A subsequently calculated from the spreading length. The calculated R₀A, obtained without requiring contact to each photodiode in the array, agrees well with electrical measurements. Asymmetry of the LBIC signals for certain devices in the arrays is shown to be a result of localized leakage at the photodiode junction or from the contact pads through the passivation layers. These results are confirmed by numerical modeling of the device structures.     

应用邻域相关处理技术的激光报警装置

介绍了作者研究设计的邻域相关处理技术.该技术能有效地提高光电二极管阵列式激光报警器分辨率,降低成本.应用这种技术设计了一台激光报警装置,通过对激光报警装置进行的原理性接收试验,证明了在相同数量的光电管下,邻域相关处理技术能成倍地提高激光报警的探测精度,邻域相关处理技术的原理是可行的.     

Monolithically integrated 1 × 12 array of planar InGaAs/InP photodiodes

We describe the fabrication and performance of monolithically integrated, 1 × 12 arrays of InGaAs/InP p-i-n photodiodes. These devices are completely optically and electrically interfaced for use in fiber-optic systems. For each element of the array, at -5 V, the dark current is <20 nA, and the total capacitance is <2.5 pF. The external coupling efficiency at 1.3 μm is >75 percent for every diode in the array. We have also measured the coupling capacitance between adjacent devices, and found it to be <0.1 pF.     

The impact of a large bandgap drift region in long-wavelengthmetamorphic photodiodes

A comparative study of two types of metamorphic double heterojunction long-wavelength photodiodes on GaAs substrates is performed in terms of their bandwidths and responsivities. A p-i-i-n heterostructure with a large bandgap drift layer (I-InAlAs) at the cathode end of the photoabsorption region (i-InGaAs) is compared experimentally and theoretically to a p-i-n structure without a drift layer. Both types of photodiodes were fabricated using an InGaAs-InGaAlAs-InAlAs double heterostructure design to simultaneously achieve high bandwidths and high responsivities. The inclusion of an I-InAlAs drift region resulted in p-i-i-n photodiodes with larger bandwidths than p-i-n photodiodes with the same areas, or conversely a p-i-i-n photodiode can be made larger than a comparable p-i-n photodiode, but achieve the same bandwidth. Therefore, p-i-i-n photodiodes provide larger optical fiber alignment tolerances and better coupling efficiency than p-i-n photodiodes with the same bandwidths, p-i-i-n photodiodes with 10-μm-diameter optical windows typically exhibited low dark currents of 500 pA at 5-V bias, responsivities of 0.6 A/W, and a -3-dB bandwidth of 38 GHz for 1.55-μm operation     

Methods for measuring the current–voltage characteristics of photodiodes in a multirow infrared photodetector

Methods for measuring the current-voltage characteristics (I–V curves) of photodiodes in a 6 × 576 mercury-cadmium-tellurium (MCT) multirow photodetector designed for operation in the longwave part of the infrared (IR) spectral range are analyzed. The I–V curve is plotted using the resultes of measurements of output signals of a large-scale readout integrated circuit (ROIC) hybridized with a row of IR photodiodes. The method of independent current measurement at each point of the I–V curve is compared to the method of additive current measurements. A method of determining optimum working points of photodiodes by plotting and analyzing the dependence of the differential resistance of photodiode on the bias voltage is proposed. Distributions of photodiode currents for a sample of a 6 × 576-element focal plane array (FPA) based on MCT photodiodes with a p-type conductivity substrate having the cutoff wavelength of λ_0.5 = 10.5 μm are considered.     

A self-scanned image sensor employing MOS structure

Studies were carried out on a self-scanned image sensor comprising a linear integrated-circuit array of photodiodes and metal-oxide-semiconductor (MOS) transistors. It was found that the maximum scanning rate is about 2.5×10⁵bits/s, and that the value is mainly restricted by the photo-induced current and the junction capacitance of the photodiode.     

Improvement in the quantum sensitivity of InAs/InAsSb/InAsSbP heterostructure photodiodes

InAs/InAs_0.88Sb_0.12/InAs_0.50Sb_0.20P_0.30 heterostructure photodiodes operating at room temperature in the spectral range 1–4.8 μm are developed. It is shown that the formation of a curvilinear reflecting surface constituted by a number of hemispheres on the rearside of the photodiode chip leads to an increase in the quantum sensitivity of the photodiodes by a factor of 1.5–1.7 at wavelengths in the range 2.2–4.8 μm. At an exposed photodiode area of 0.9 mm² and a p-n junction area of 0.15 mm², a zero-bias differential resistance of 30 Ω and a quantum sensitivity of 0.24 electron/photon at a wavelength of 3 μm are obtained. The operation of a photodiode with re-reflection of the photon flux in the crystal due to reflection from the curvilinear surface of the rearside of the photodiode chip is theoretically analyzed. The possibility of effective conversion of the re-reflected flux of photons into a photocurrent, with a simultaneous decrease in the p-n junction area, is demonstrated. An increase in the quantum sensitivity in the short-wavelength spectral range 1–2.2 μm by 35% relative to the calculated data is observed, which is probably due to impact ionization in the narrow-gap active region.     

UHF photoparametric amplifier

Measurements on a degenerate UHF photoparametric amplifier using an optical signal modulated at 690 MHz have confirmed the 3 dB noise figure predicted by Penfield and Sawyer. The silicon photoparametric diode served as both the photodetector and varactor and was novel in several respects: the conductivity sequence was p-v-n-n⁺in contrast to the usual p-v-n⁺conventionally used for microwave photodiodes; and the diode was designed to be illuminated parallel to the p-v junction. Such a structure has an inherently high Q and features are extended optical response (quantum efficiency ≈ 10 percent at 1.06 µ), coupled with good UHF photodetection behavior, when used either as a simple (unpumped) photodiode or as a photoparametric diode.     

Dual-phase synchronous light detection with 64/spl times/64 CMOS modulated light camera

A scalable sensor for wide field detection (imaging) of low contrast amplitude-modulated light has been fabricated in a standard CMOS process. The sensor has a randomly addressable array of 64/spl times/64 feedback buffered photodiodes. Any row of the photodiode array can be connected to 64 independent dual-phase lock-in detection channels allowing two-dimensional phase sensitive imaging without mechanical scanning.     

A Ga0.47In0.53As/InP heterophotodiode with reduced dark current

We have used a Ga0.47In0.53As/InP heterostructure to produce a photodiode (area =3 times 10^{-4}cm²) which shows a saturated dark current of 100 pA at 23°C and 1.7 nA at 50°C. At this dark current, these photodiodes have near-unity quantum efficiency at 1.6 μm and show good photoresponse over the1.0-1.65 mum region of the optical spectrum.     

Monolithic vertical-cavity laser/p-i-n photodiode transceiver arrayfor optical interconnects

The design, fabrication, and characterization of a 16-element monolithic 850-nm vertical-cavity laser/p-type-intrinsic-n-type (VCL/p-i-n) photodiode transceiver array for optical interconnects are described. The packaged VCL/p-i-n array exhibits excellent array uniformity over a large temperature range. Packaged VCLs display up to 1 mW of single-mode power and a relative intensity noise below -120 dB/Hz for all currents above threshold at a measuring bandwidth of 2 GHz. The p-i-n photodiodes exhibit a responsivity of 0.535 A/W and a -3-dB bandwidth of 2.3 GHz. A microlens array integrated into the packaged VCL/p-i-n device decreases the VCL beam divergence six to seven times. Polarization control with a mean rejection ratio of 22 dB across the VCL array is achieved with the use of oval aperture VCLs     

An Experimental 50 Mb/s Fiber Optic PCM Repeater

An experimental repeater for amplification and regeneration of 50 Mb/s fiber-optical pulses has been built and tested. For the receiver either Si p-i-n or avalanche photodiodes are used in conjunction with a high impedance FET input amplifier. The high voltage for the avalanche photodiode is generated internally and controlled by the received signal. This AGC circuit is capable of compensating for temperature changes of the avalanche gain over the range of-40 - +60degC. The optical transmitter consists of either a GaAs light emitting diode or a GaA1As laser diode coupled to optical fibers and directly modulated by a current driver with 30 percent electrical efficiency. For 10^-9error rate, the required average optical signal power for a pseudorandom signal is p-i-n diode: -41.5 dBm; avalanche diode: -56.6 dBm. The optical output power into a fiber with 1 percent index difference is LED: -17 dBm; GaAlAs laser: 0 dBm. The repeater power requirement is about 2 W.