Avalanche behavior of power MOSFETs under different temperature conditions

The ability of high-voltage power MOSFETs to withstand avalanche events under different temperature conditions are studied by experiment and two-dimensional device simulation.The experiment is performed to investigate dynamic avalanche failure behavior of the domestic power MOSFETs which can occur at the rated maximum operation temperature range(-55 to 150℃).An advanced ISE TCAD two-dimensional mixed mode simulator with thermodynamic non-isothermal model is used to analyze the avalanche failure mechanism.The unclamped inductive switching measurement and simulation results show that the parasitic components and thermal effect inside the device will lead to the deterioration of the avalanche reliability of power MOSFETs with increasing temperature.The main failure mechanism is related to the parasitic bipolar transistor activity during the occurrence of the avalanche behavior.     

雪崩光电探测器的击穿效应模型分析

基于CMOS工艺制备了空穴触发的Si基雪崩探测器(APD),基于不同工作温度下器件的击穿特性,建立空穴触发的雪崩器件的击穿效应模型。根据雪崩击穿模型和击穿电压测试结果,拟合曲线得到击穿电场与温度的关系参数(dE/dT),器件在250～320 K区间内,击穿电压与温度是正温度系数,器件发生雪崩击穿为主,dV/dT=23.3 mV/K,其值是由倍增区宽度以及载流子碰撞电离系数决定的。在50～140 K工作温度下,击穿电压是负温度系数,器件发生隧道击穿,dV/dT=-58.2 mV/K,其值主要受雪崩区电场的空间延伸和峰值电场两方面因素的影响。     

Low dark current GaN avalanche photodiodes

We report the fabrication and characterization of GaN avalanche photodiodes grown on sapphire by metalorganic chemical vapor deposition. Current-voltage characteristics indicate a gain higher than 23. The photoresponse is independent of the bias voltage prior to the onset of avalanche gain which occurs at an electric field of ~4 MV/cm. Near avalanche breakdown, the dark current of a 30-μm diameter device is less than 100 pA. The breakdown shows a positive temperature coefficient of 0.03 V/K that is characteristic of avalanche breakdown     

DC thermal model of semiconductor device produces current filaments as stable current distributions

How current filaments arise in semiconductor devices can be studied with the aid of a simple two-dimensional thermal model. This dc model generates temperature and current distributions across the semiconductor chip. To use the model one must be able to prescribe the temperature dependence of the dc conductance in the chip from prior knowledge of the conduction mechanism. This model produces current filaments as stable current distributions. Moreover it demonstrates that current filaments will form in avalanche diodes at high power levels even if the chips are defect-free. The key to filament formation in a semiconductor device is an increase of the dc conductance with temperature at some operating point. In avalanche conduction, when the diode bulk leakage current increases faster than the avalanche current multiplication factor decreases with temperature, the avalanche conductance begins to rise. When this happens, a current filament forms raising the temperature locally to more than 1600°C, according to the model, and results in diode burnout. This mechanism is believed to be involved also in RF-induced burnout of avalanche diodes and in the burnout of other semiconductor devices.     

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     

AlGaN日盲紫外雪崩光电探测器暗电流研究

为了提高AlGaN日盲紫外雪崩探测器的信噪比,降低暗电流,研制高性能日盲紫外探测器,针对AlGaN日盲紫外雪崩探测器暗电流机制进行了深入研究。首先对传统p-i-n-i-n结构雪崩探测器进行了初步研究,分别设计了GaN和AlGaN的两种雪崩探测器模型,分析了其不同暗电流特性,得到的模拟暗电流特性曲线与实验吻合。在此基础上,针对日盲紫外波段高Al组分AlGaN雪崩探测器,重点分析研究了不同异质界面的负极化电荷、p型有效掺杂以及温度等因素对暗电流的影响。在AlGaN日盲紫外雪崩探测器研究中得到的近零偏工作暗电流为2.510-13 A,在反向138 V左右发生雪崩击穿,雪崩开启电流为18.3 nA左右,击穿电压温度系数约为0.05 V/K,与实验及文献测试结果吻合。     

雪崩管最佳倍增因子线性化温控技术研究

为了进一步增强机载激光测距机在全温范围内的环境适应性,分析了温度与探测器模块输出功率信噪比的关系,推导了最佳倍增因子与温度的方程式,阐述了温度变化引起倍增因子对最佳雪崩倍增因子偏离的原因。根据雪崩管探测器雪崩击穿电压的线性温度特性,设计了机载温度范围为-55℃~70℃的基于自然对数法的最佳倍增因子雪崩偏压线性化温控电路,用于补偿因温度变化所引起的倍增因子对最佳雪崩倍增因子的偏离。结果表明,实测雪崩偏压温控系数为2.29V/℃,与理论分析值误差仅为4%。该技术用于新型机载激光测距系统中,获得了良好的试验数据,满足机载环境的特殊需求。     

雪崩光电二极管最佳偏置电路

文中对雪崩光电二极管的温度影响因素作了一般性讨论,给出了几种稳定方式.文中简要介绍了雪崩光电二极管的倍增噪声电流谱密度与等效输入噪声电流谱密度推出的结果.根据结论进行最佳倍增稳定偏置电路设计,给出了参考电路.使用这种自动偏置最佳状态电路,使探测系统性能大为改善.     

Analysis of temperature dependence of linearity for SiGe HBTs in the avalanche region using Volterra series

In this paper, linearity characteristic of silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) at different temperatures in the avalanche regime is investigated by the Volterra approach incorporating with a physics-based breakdown network for the first time. Third-order intermodulation distortion (IMD₃) decreases with increasing temperature in the impact ionization region due to lower nonlinear contributions from individual nonlinearity according to the Volterra analysis results. Calculated gain, output power, and efficiency of SiGe HBTs are in good agreement with measurement results in the avalanche region. This analysis with respect to temperature can benefit the reliability study of linearity for SiGe HBTs in the avalanche regime.     

Low-noise visible-blind UV avalanche photodiodes with edgeterminated by 2° positive bevel

4H-SiC avalanche photodiodes edge terminated by a 2° positive bevel have been fabricated and characterised. Low leakage current, positive temperature dependence of breakdown voltage, high avalanche gain and very low noise have been achieved     

Design considerations for 1.06-/spl mu/m InGaAsP-InP Geiger-mode avalanche photodiodes

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-/spl mu/m 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.     

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

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-$muhbox m$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.     

Operation of SiC normally-off JFET at the edges of its safe operating area

The paper presents the results of an experimental characterization about the operation of the last-generation normally-off SiC JFETs at the edges of their safe operating area. Short circuit and unclamped turn-off operations have been investigated by means of a nondestructive experimental set up where the device is switched in the presence of a protection circuit capable of limiting the energy dissipated on the device after the failure occurrence. The experimental results confirm the very good performances of the device in short circuit for which the failure can be associated only to the increase of the temperature over the limits imposed by the surface metallization. A different scenario appears for the unclamped tests where a second breakdown occurs after a quite long avalanche phase followed by the device failure. It is demonstrated that the duration of the avalanche phase depends on the temperature of the device under test. The damaged area after an avalanche failure is localized at the edge termination of the device and, in particular, at the corner between source and gate metallization.     

Intrinsic response time measurements in uniform and nonuniform field avalanche regions in GaAs

Experimental determination of the intrinsic avalanche response time τ1in GaAs microwave diodes shows good agreement with theoretical predictions for structures having uniform electric fields in the avalanche region as opposed to those with nonuniform profiles. Measurements are presented for a high-power GaAs double-drift Read diode, a single drift X-band Read diode and a 35-GHz Lo-Hi-Lo bathtub structure to demonstrate the agreement. The agreement of these results with calculations that neglect high field diffusion indicates that high field diffusivity is not very important in GaAs avalanche regions as narrow as 2000 Å. The value of τ1, for the high-power double-drift diode obtained from high-frequency noise measurements, was found to be in agreement with the value obtained for the same diode by Adlerstein et al., where τ1was obtained from microwave admittance data. Experiments indicate that observed variations in the value of τ1due to changes in the junction temperature are consistent with variations due to the temperature dependence of the scattering limited velocities. It is further concluded that consistent discrepancies found between theory and experiment for structures having nonuniform fields in the avalanche region are the result of nonlocal effects in GaAs.     

MBE-grown HgCdTe multi-layer heterojunction structures for high speed low-noise 1.3–1.6 µm avalanche photodetectors

HgCdTe is an attractive material for room-temperature avalanche photodetectors (APDs) operated at 1.3–1.6 μm wavelengths for fiber optical communication applications because of its bandgap tunability and the resonant enhancement of hole impact ionization for CdTe fractions near 0.73. The HgCdTe based separate absorption and multiplication avalanche photodetector is designed and fabricated for backside illumination through a CdZnTe substrate. The multi-layer device structure is comprised of seven layers including 1). n ⁺ contact 2). n ⁻ diffusion buffer 3). n ⁻ absorber 4). n charge sheet 5). n ⁻ avalanche gain 6). p to form junction, and 7).p ⁺ contact. Several wafers were processed into 45 μm × 45 μm and 100 (μm × 100 μm devices. The mean value of avalanche voltage is 63.7 V measured at room temperature. At 1 GHz, the device shows a gain of about 7 for a gain-bandwidth product of 7 GHz. This first demonstration of an all molecular beam epitaxially grown HgCdTe multi-layer heterojunction structure on CdZnTe substrates represents a significant advance toward the goal of producing reliable room temperature HgCdTe high speed, low noise avalanche photodetectors.     

Temperature dependence of snap-back breakdown up to 300°C analyzed using circuit level model and simulation

The MOS snap-back breakdown and its temperature dependence were investigated up to 300°C using silicided LDD-NMOS transistors. The snap-back sustaining voltage increases from 8.25V at room temperature to 8.9V at 300°C (for L_eff=0.56μm). By using extracted parameters for a simple lumped element model we explain this behaviour originating from an increasing avalanche breakdown voltage and slope of avalanche multiplication factor compensating the increase in bipolar gain with temperature.     

Ultraviolet Single Photon Detection With Geiger-Mode 4H-SiC Avalanche Photodiodes

We report 4H-SiC avalanche photodiodes operated in Geiger mode for single photon detection at 265 nm. At room temperature, the single photon detection efficiency is 14% with a dark count probability of 1.7 x 10^-4. Since the external quantum efficiency is 21% at 265 nm, it follows that 65% of the absorbed photons are counted as avalanche events. The jitter of the photodiodes is also characterized.     

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.     

高速近红外1550nm单光子探测器

高速近红外1 550 nm单光子探测器采用半导体制冷和热管风冷混合技术,雪崩二极管工作于盖革模式下,使用交流耦合方式提供门脉冲信号,通过延迟补偿和采样边沿锁存方式消除尖脉冲干扰,采用反馈门控减小后脉冲的影响。采用了ECL(Emitter Couple Logic)与TTL(Transistor-TransistorLogic)混合电子技术提高单光子探测系统的运行频率,其频率可大于10 MHz;另外,通过对雪崩信号的放大来提高信号的动态范围,进一步优化探测器的性能。实验测试与分析表明,探测器在时钟频率10 MHz、温度-62℃、门脉冲宽度8 ns的条件下的最优性能参数为:量子探测效率12.8%,暗计数率3.76×10-6ns-1,噪声等效功率8.68×10-19W/Hz1/2。     

电子倍增型GaAs光阴极实验研究

电子倍增型GaAs光阴极是利用雪崩倍增效应的一种新型光阴极组件,通过在常规GaAs光阴极中引入雪崩电子倍增层制备了GaAs光阴极/电子倍增器一体化组件,研究了该组件的热清洗温度、电子增益等性能.对组件热清洗工艺前后的I-V特性进行了对比测试,结果表明,该组件可以承受580℃的热清洗温度,并获得了12.6倍的电子增益;880nm处的探测灵敏度≥3.87mA/w;暗电流密度≤6.79×10^-5mA/cm².