Low avalanche noise characteristics in thin InP p+-i-n+ diodes with electron initiated multiplication

We have performed electron initiated avalanche noise measurements on a range of homojunction InP p⁺-i-n⁺ diodes with “i” region widths, w ranging from 2.40 to 0.24 μm. In contrast to McIntyre's noise model a significant reduction in the excess noise factor is observed with decreasing w at a constant multiplication in spite of α, the electron ionization coefficient being less than β, the hole ionization coefficient. In the w=0.24 μm structure an effective β/α ratio of approximately 0.4 is deduced from the excess noise factor even when electrons initiate multiplication, suggesting that hole initiated multiplication is not always necessary for the lowest avalanche noise in InP-based avalanche photodiodes     

Extremely Low Excess Noise in InAs Electron Avalanche Photodiodes

Measurements of the avalanche multiplication noise in InAs p-i-n and n-i-p diodes at room temperature demonstrate unambiguously that the avalanche multiplication process is dominated by impact ionization of electrons. This results in the excess noise factor for electron initiated multiplication asymptotically approaching a maximum value just less than two and becoming virtually gain-independent for higher gains. Measurements for predominantly hole initiated multiplication show corresponding high excess noise factors suggesting the electron to hole ionization coefficient ratios are comparable to those reported for $hbox{Hg}_{1-{x}}hbox{Cd}_{x}hbox{Te}$ electron avalanche photodiodes.      

On the avalanche initiation probability of avalanche diodes above the breakdown voltage

In the calculation of the turn-on probabilities per unit time of avalanche diode microplasmas, or of the single-photon detection probabilities of avalanche photodiodes used in the photon-counting mode, it is desirable to know how the avalanche initiation probability varies with voltage above the breakdown voltage. It is shown that the two coupled differential equations derived by Oldham et al. for the probabilities that a self-sustaining avalanche will be initiated in an avalanche diode biased above the breakdown voltage by an injected electron or by an injected hole (avalanche initiation probabilities) can be combined to provide a single integral equation for each of the electron, hole, and electron-hole pair initiation probabilities. These equations can be integrated for the special case in which the electron and hole ionization rates αeand αhare related byalpha_{h} approx kalpha_{e}wherekis a constant. A method of computing an effective value ofkfor other cases in which this approximation is not a good one is presented. The resulting expressions are shown to be consistent with previously published calculations by McIntyre of the breakdown probabilities both for the casek = 1and for the more general casek neq 1.     

Experimental investigation of ultrashort pulse laser-inducedbreakdown thresholds in aqueous media

Laser-induced breakdown (LIE) thresholds are determined for pulse durations of 2.4 ps, 400 fs, and 100 fs at 580 mn in high purity water, saline and tap water. The dependence of LIE irradiance thresholds on pulse duration, optical wavelength, and focal volume is examined, and the experimental data obtained is compared with a theoretical model. The slopes of the probability curves calculated are compared with mechanisms for LIE, namely avalanche ionization, multiphoton initiated avalanche ionization, and multiphoton ionization. Lastly, the dependence of the peak breakdown electric field on pulse duration and focal volume is empirically determined and compared with previous work     

超短脉冲激光对无机硅材料的损伤

通过控制作用于材料表面的激光能量和脉冲数量,实验研究了800nm,50fs,1kHz激光作用下融石英玻璃和硅片的破坏机制和损伤规律,计算了材料的损伤阈值与脉冲能量以及脉冲数量的依赖关系,并采用简化的理论模型计算了熔石英玻璃材料的损伤阈值与激光脉宽以及光子能量之间的依赖关系。对这两种无机硅材料在飞秒脉冲作用后的微区结构改变进行了扫描电子显微镜(SEM)测试,研究了其形貌特征。结果表明,硅片是由缺陷中的导带电子作为种子电子引发雪崩电离导致材料损伤,而熔石英玻璃是由多光子电离激发出导带电子引发雪崩电离导致材料损伤。     

Modes of avalanche oscillations in silicon diodes

A computer program which includes both electronic and thermal processes has been used to study avalanche oscillations in a diode which is punched through only well above breakdown. IMPATT, relaxing avalanche, and MULTIPATT oscillations have been studied. The MULTIPATT mode is shown to be a superpesition of transit-time oscillations upon a relaxation oscillation. It is postulated that the TRAPATT mode is initiated by the IMPATI mode via the MULTIPATI mode. The frequency of the IMPATT oscillations was found to vary with the square root of the current over a factor of 100 in current. For parallel operation of TRAPATT diodes, it is shown that nonpunched-through diodes should be used.     

Avalanche noise characteristics of thin GaAs structures withdistributed carrier generation [APDs]

It is known that both pure electron and pure hole injection into thin GaAs multiplication regions gives rise to avalanche multiplication with noise lower than predicted by the local noise model. In this paper, it is shown that the noise from multiplication initiated by carriers generated throughout a 0.1 μm avalanche region is also lower than predicted by the local model but higher than that obtained with pure injection of either carrier type. This behavior is due to the effects of nonlocal ionization brought about by the dead space; the minimum distance a carrier has to travel in the electric field to initiate an ionization event     

Boundary effects on multiplication noise in thin heterostructure avalanche photodiodes: theory and experiment [Al/sub 0.6/Ga/sub 0.4/As/GaAs]

The history-dependent recurrence theory for multiplication noise in avalanche photodiodes (APDs), developed by Hayat et al., is generalized to include inter-layer boundary effects in heterostructure APDs with multilayer multiplication regions. These boundary effects include the initial energy of injected carriers as well as bandgap-transition effects within a multilayer multiplication region. It is shown that the excess noise factor can be significantly reduced if the avalanche process is initiated with an energetic carrier, in which case the initial energy serves to reduce the initial dead space associated with the injected carrier. An excess noise factor reduction up to 40% below the traditional thin-APD limit is predicted for GaAs, depending on the operational gain and the multiplication-region's width. The generalized model also thoroughly characterizes the behavior of dead space as a function of position across layers. This simultaneously captures the effect of the nonuniform electric field as well as the anticipatory nature of inter-layer bandgap-boundary effects.     

Current mode second breakdown in epitaxial planar transistors

Current mode second breakdown is a type of voltage "switchback" observed in epitaxial transistors. The phenomenon is initiated when the emitter is injecting at a collector voltage in excess of the collector-emitter sustaining voltage, and is characterized by delay and voltage fall times on the order of a nanosecond. The device can be sustained in the low voltage state only as long as there is sufficient charge to produce conductivity modulation within the collector-base depletion region. When the available charge is exhausted, the collector voltage will recharge at a rate determined by the external circuit. At some critical current density, the collector-base depletion region collapses toward the high conductivity substrate. The electric field within the depletion region increases as the depletion region width narrows, until avalanche occurs. The sustaining voltage will be determined by the bulk base-to-collector avalanche voltage. A consequence of this behavior is that most epitaxial transistors cannot operate stably in the LVCERmode, and switching-off unclamped inductive circuits with the emitter-base junction terminated in some finite resistance will lead to second breakdown.     

A Monte Carlo investigation of multiplication noise in thin p+-i-n+ GaAs avalanche photodiodes

A Monte Carlo (MC) model has been used to estimate the excess noise factor in thin p⁺-i-n⁺ GaAs avalanche photodiodes (APD's). Multiplication initiated both by pure electron and hole injection is studied for different lengths of multiplication region and for a range of electric fields. In each ease a reduction in excess noise factor is observed as the multiplication length decreases, in good agreement with recent experimental measurements. This low noise behavior results from the higher operating electric field needed in short devices, which causes the probability distribution function for both electron and hole ionization path lengths to change from the conventionally assumed exponential shape and to exhibit a strong dead space effect. In turn this reduces the probability of higher order ionization events and narrows the probability distribution for multiplication. In addition, our simulations suggest that fur a given overall multiplication, electron initiated multiplication in short devices has inherently reduced noise, despite the higher feedback from hole ionization, compared to long devices     

Effect of avalanche build-up time on avalanche photodiode sensitivity

A calculation method for the receiver sensitivity of an avalanche photodiode is considered, taking into account avalanche build-up time and carrier transit time, in addition to the CR time constant. Actual receiver performance is estimated in a high data rate region of up to 10 Gbits/s for germanium avalanche photodiodes, applying the measured avalanche build-up time.     

A simplified non-Gaussian approach to digital optical receiverdesign with avalanche photodiodes: theory

A simplified theory of avalanche photodiode receiver sensitivity is presented in which the non-Gaussian nature of the avalanche multiplication process is taken into account. The theory predicts more accurately than a Gaussian theory the optimum avalanche gain and decision threshold and gives simple results for the influence of background photocurrent or dark current on receiver sensitivity, optimum gain, and threshold. For purposes of comparison, a parallel derivation using the Gaussian approximation for both the avalanche and receiver noises is given where simple expressions for the optimum avalanche gain and threshold settings are derived     

Impact ionization resonance and auger recombination in Hg1 - xCdxTe (0.6 ≤ x ≤ 0.7)

The purpose of this paper is the study of the impact ionization and the Auger recombination in Hg1-xCdxTe avalanche photodiodes, with0.6 leq x leq 0.7. Forx sim 0.7it is shown that the spin orbit splitting Δ is lower than the bandgap energy Egso that impact ionization is initiated by holes from the Split-off valence band. Forx sim 0.6, Delta sim E_{g}, the rate of the Auger recombination is maximum, corresponding to a resonant impact ionization and to a maximum ratiok = beta / alphawhere α and β are, respectively, the impact ionization coefficient for electrons and holes.     

High-frequency properties of avalanche multiplication of photocarriers in structures with negative feedback

The high-frequency characteristics of photosensitive avalanche Si-SiC structures were studied. It is shown that their high-speed operation is substantially superior to that of silicon avalanche photodiodes. A theoretical analysis of the high-frequency properties of avalanche photodiodes is carried out and analytical expressions for the gain-bandwidth product are obtained. It is shown that this product is not a universal parameter for a metal-insulator-semiconductor structure with a negative feedback, since, for high amplification factors, the effective value of the relation of the impact-ionization coefficients for different types of charge carriers in such structures turns out to be significantly different from that in avalanche photodiodes.     

Avalanche behavior of low-voltage power MOSFETs

This letter addresses the behavior of low voltage power MOSFETs under avalanche, with a paralleling point of view. It is shown that during avalanche, up-to-date technology MOSFET transistors exhibit a resistance far in excess of their on-state resistance (R/sub DSon/). A novel test setup is proposed to measure "avalanche" resistance. A simple model of breakdown voltage is then proposed. It becomes possible to perform fast simulations using this model to study current balance between paralleled transistors under avalanche operation. It is shown that considering avalanche resistance reduces the influence of breakdown voltage mismatches and allows for better current sharing.     

关于雪崩结开启电压和关断电压差别的研究

本文详细研究了雪崩结导通电压和关断电压的差别。 当结特征尺度在微米量级时,这个差别将不能忽略, 这个结果与现有报道不一致,并且对对器件参数的正确表征有较大影响。 实验发现当结面积变小时, 这个差别将增大。 本文对该现象进行了分析, 给出了理论解释,认为这个现象是由于结导通的阈值增益随着结面积的减小而增加的缘故。在雪崩渐近电流公式中, 所谓的“击穿电压”实际上应该是雪崩结关断电压。 修正了传统的关于雪崩渐近电流和盖革模式雪崩光电二极管的增益公式。     

Characterization and modeling of avalanche multiplication in HBTs

The accurate modeling of weak avalanche breakdown of HBTs in compact bipolar transistor models for circuit simulation is presented. Based on various device electrical characteristics that are grouped into three classes, a modified VBIC avalanche multiplication model is proposed. By simply replacing one constant avalanche model parameter with current linear dependence, the new model predicts well broad behaviors of breakdown from weak avalanche up into high level injections.     

Avalanche multiplication in a compact bipolar transistor model forcircuit simulation

A simple weak avalanche model valid in a wide range of voltages and currents, is presented. The proposed model is derived by using the base-collector depletion capacitance for predicting the avalanche current. The model needs only one additional transistor parameter; the extraction method and temperature dependence of this parameter are discussed. The decrease in avalanche current for high collector current densities may originate from internal device heating, a voltage drop in the epilayer, or mobile carriers in the depleted part. From experimental results it is concluded that, below a critical hot-carrier current, the decrease in avalanche current due to mobile carriers is negligible     

On the trigger delay of avalanche transistors

An explanation of the triggering delay in avalanche transistors is given, based on the results of a numerical model for the avalanche transistor. The results obtained allow one to modify the delay by very simple means as it is needed when several avalanche stages are paralleled.     

Si-controlled avalanche logic

It is proposed that a new integrated-circuit logic system, based on the controlled avalanche mechanism in Si, be developed to meet high speed data processing needs in the multigigabit rate range. A brief discussion of the "controlled avalanche" mechanism is given, and past experimental results with "controlled avalanche transit-time triodes" are cited. The role of avalanche multiplication in increasing the speed over a transistor of the same dimensions is explained. A short drift length "controlled avalanche transistor" (CAT) could be developed to increase the speed of Si logic beyond the present limited capability. To fully exploit the avalanche mechanism, new circuit configurations are proposed which are comprised of CAT's and avalanche diodes to function as NOR, NAND, and INVERT gates. Moreover, a latching action can be obtained in the CAT by means of the return hole mechanism and the device becomes an avalanche memory triode (AMT). Such AMT's are natural devices for shift-register circuits and random-access memory applications. The controlled avalanche logic family of devices, therefore, contains all necessary building blocks for a fast data handling system. It is estimated that a data rate of the order of gigabits per second with a P. t product of the order 10^-12J is possible. Experimental results on discrete devices are presented to demonstrate the switching, memory, and transfer capabilities of the device.