Radiation Effects in Gaas Junction Field-Effect Transistors

GaAs field-effect transistors for linear and digital circuits are finding applications in systems that have to function in a nuclear environment. This paper reviews and analyzes the radiation damage mechanisms in GaAs material and applies the material parameter changes to predict changes of electrical parameters of junction field-effect transistors due to exposure to fast neutrons and total dose ionizing radiation. The transient response to pulsed ionizing radiation is analyzed and experimental results are correlated with theoretical predictions. Annealing characteristics of radiation-generated defects are described. The prospects for hardening GaAs fieldeffect transistor integrated circuits against the effects of nuclear radiation are assessed.     

Total ionizing dose effects in high voltage devices for flash memory

The effect of size and substrate bias conditions after irradiation on the total ionizing dose response of high voltage devices for flash memory has been investigated. Different sensitivity of transistors with different gate width was observed, which is well known as the radiation induced narrow channel effect. A charge sharing model was used to explain this effect. The negative substrate bias voltage after irradiation showed considerable impact on the parasitic transistor’s response by suppressing leakage current.     

Modeling Rapid Annealing in Digital Integrated Circuits

An analytical model for the effects of rapid annealing in narrow base bipolar transistors has been developed. This model utilizes transistor base-emitter voltage and an empirical curve to calculate annealing factor with time. The model has been incorporated into the TRAC circuit analysis code and used to predict the time-dependent response of a low-power Schottky TTL NAND gate and a four-bit shift register as a function of neutron fluence and operating condition.     

Radiation Effects on Junction Field Effect Transistors

Experimentally determined permanent and transient effects of radiation on the electrical characteristics of junction field effect transistors (JFET's) are presented for JFET's exposed to energetic neutron doses up to 1016 neutrons/cm2 (E > 10 Kev) and ionizing radiation up to 8×109 rad/sec. Results of extensive transient radiation experiments using the AFCRL Linac are presented for various combinations of channel doping, gate resistor values, gate voltages, drain voltages, gold doping and dose rates. Limited new experimental data is presented on neutron damage. Existing neutron degradation data on hardened JFET's is summarized. The JFET neutron degradation theory is summarized and refined.     

Optimization of the Neutron Radiation Tolerance of Junction Field Effect Transistors

The fast neutron irradiation induced degradation of junction field effect transistors has been studied in detail. A comparison of p-channel to n-channel devices has confirmed reported differences in hole and electron removal rates. The predicted increase of hardness with increasing channel dopant concentration is experimentally demonstrated, although channel dopant grading makes very heavily doped units difficult to attain in practice. Also, a device modification which allows attainment of breakdown voltages higher than those characteristic of the channel doping level is presented and experimentally verified. This modification made possible the construction of devices with breakdown voltages greater than fifty volts, which degraded by only 25% in transconductance at fluences of approximately l-3×1015 neutrons/cm2 (E > 10 kev, Triga). Thus, the technique offers promise in the construction of very radiation resistant devices with wide operating voltage ranges.     

不同偏置对NPN双极晶体管的低剂量率电离辐照损伤的影响

对NPN双极晶体管进行了低剂量率下不同偏置条件的电离辐射实验。结果表明,不同偏置条件下的低剂量率辐射损伤具有明显差异。基-射结反向偏置时,其过剩基极电流最大,电流增益衰减最为显著。而基-射结正向偏置时,过剩基极电流和电流增益衰减都最小。讨论了出现这种结果的内在机制。     

Effects of space radiation damage and temperature on the noise inCCDs and LDD MOS transistors

Lightly doped drain (LDD) MOS transistors were subjected to proton radiation damage representative of the damage they would receive on a typical orbital space telescope mission. The noise spectral density was measured as a function of gate voltage, temperature and total radiation dose. These data were used to model the resultant noise lower limit read for that transistor when used as the charge-conversion, output stage of a charge-coupled-device (CDD) imaging array detector. Very clear evidence of excess noise being added to the CCD output as a function of radiation was found. It is possible to select combinations of temperature, CCD dual-correlated sample time constant and gate voltage which minimize the performance degradation due to this excess noise     

Investigation of sensitivity and threshold voltage shift of commercial MOSFETs in gamma irradiation

This article is about the absorbed-dose-dependent threshold voltage shift of the MOSFET transistors.Performance of the MOSFETs has been tested in different gate voltages.Sensitivity of the transistors for 662 ke V gamma ray is studied in 1–5 Gy dose range.It was found that for transistors irradiated in biased mode,significant changes in the threshold voltage occurred,and the sensitivity to gamma rays increased with the bias voltage.     

Total Dose Indujced Hole Trapping and Interface State Generation in Bipolar Recessed Field Oxides

Ionizing radiation induced trapped hole density, Not, and interface state density, Nit, are investigated in bipolar recessed field oxides using parasitic nMOS transistors. Most of the results agree with previous studies made with capacitors on generic thick field oxides. New results include the effects of PN junction fringing fields on inversion voltage shift. Implications are made for total dose failure of bipolar microcircuits based on results of inversion voltage shift versus channel length and channel doping density. under contract DNA001-83-C-0115.     

Thin Film Silicon on Silicon Nitride for Radiation Hardened Dielectrically Isolated Misfet's

The permanent ionizing radiation effects resulting from charge trapping in a silicon nitride isolation dielectric has been determined for a total ionizing dose up to 107 rads (Si). Junction FET's, whose active channel region is directly adjacent to the siliconsilicon nitride interface, were used to measure the effects of the radiation induced charge trapping in the Si3N4 isolation dielectric. The JFET saturation current and channel conductance versus junction gate voltage and substrate voltage were characterized as a function of the total ionizing radiation dose. The experimental results on the Si3N4 are compared to results on similar devices with SiO2 dielectric isolation. The ramifications of using the silicon nitride for fabricating radiation hardened dielectrically isolated MIS devices are discussed.     

Dose-Rate Effects in the Permanent Threshold Voltage Shifts of MOS Transistors

Data has been collected that shows the permanent threshold voltage shift occurring in MOS transistors exposed to the same total dose of gamma radiation can be greater in a high dose-rate environment than in a low dose-rate environment. This dose-rate effect is ascribed to a "Photovoltaic" bias generation in the substrate of a device which results in an effective gate bias change (positive for P-channel and negative for N-channel transistors). The bias change ranges from 0 to ±1 volt during the radiation burst. Thus, in a high dose-rate ionizing environment, the permanent gate threshold voltage shift of an MOS device, which is known to be a function of the gate bias during irradiation, will exhibit an indirect dose-rate dependence which is caused by an internal change in instantaneous gate bias.     

0.18 μm MOS差分对管总剂量失配效应研究

为明确深亚微米MOS差分对管在电离辐射环境下晶体管失配表征方法及损伤机理,本文针对0.18 μm NMOS、PMOS差分对管,进行了⁶⁰Co γ总剂量辐射效应研究。研究结果表明：与PMOS差分对管相比,NMOS差分对管对总剂量辐照更敏感,主要表现在：1) 辐照引起NMOS差分对管转移特征曲线失配增加;2) NMOS差分对管阈值电压失配随辐照总剂量的增加而增大;3) 栅极电流辐照后稍有增加,失配随栅极电压的增加而增大。而PMOS差分对管在整个辐照过程中,无论是曲线还是参数均未出现明显变化,且失配亦未随辐照总剂量的增加而增大。     

Generalized Model Analysis of Ionizing Radiation Effects in Semiconductor Devices

The necessity of analyzing complex semiconductor device behavior in the radiation environment requires improved analytical methods for accurate representation. The purpose of this discussion is to present work done on the applicability of the Linvill lumped model in a generalized model analysis. The advantages of the lumped model technique include flexibility in detail of device representation (i.e., accuracy), an intimate coupling to the well known radiation effects in bulk semiconductor material, and a unified analytical technique for a wide range of devices. It is shown that the lumped model analysis provides an effective technique for analyzing simple as well as complex devices in a pulsed ionizing radiation environment. Included is the representation of a simple p-n junction diode, a grown-junction transistor; and a planar-diffused transistor with its monolithic-chip substrate and isolation junction. The lumped-model behavior of the diode and grown junction transistor is compared to previously available analytical results. Using measured parameter values, the quantitative lumped-model predictions are compared to experimentally observed transient radiation response. The transistor response is investigated as a function of quiescent emitter current and external base resistance. The effect of the substrate junction in the monolithic-chip transistor is qualitatively presented as a function of the transistor parameters and the substrate proximity.     

Hybrid Photomultiplier Tubes Using Internal Solid State Elements

A new family of photomultiplier tubes has been developed using silicon diodes and transistors as multiplying elements. For applications requiring low and medium gains these tubes offer several advantages over tubes utilizing ordinary dynode multiplication. These include ease of fabrication, mechanical ruggedness, reduced sensitivity to magnetic fields, and fast response. Diode structures have provided normal gains up to the theoretical maximum and have exhibited very short response times. In a few cases anomalously high diode gains have been observed, apparently as the result of induced avalanching near the diode front surface. Much greater gains have been obtained from various transistor structures with some sacrifice in the response time.     

Effects of total-dose irradiation on gate-all-around (GAA) devices

The response of gate-all-around (GAA) MOS transistors to dose irradiation is quite different from that observed on other types of silicon-on-insulator (SOI) MOSFETs. In regular SOI MOSFETs, edge leakage increases substantially faster than the main transistor leakage upon creation of oxide charges due to the irradiation. The GAA MOSFET behaves in the opposite way; the shift of edge threshold voltage upon creation of charges in the oxide is smaller than that of the main transistor. As a result, a kink develops in the subthreshold characteristics of regular SOI MOSFETs upon irradiation, while the original subthreshold kink of GAA devices disappears when the device is irradiated     

Total gamma dose characteristics of CMOS devices in SOI structuresbased on oxidized porous silicon

The electrical characteristics of complementary metal-oxide-semiconductor (CMOS) transistors and ring oscillators fabricated in porous silicon silicon-on-insulator (SOI) structures are presented before and after gamma irradiation. P-channel SOI/MOS transistors exhibit a front-gate threshold voltage shift of -0.2 and -0.55 V after exposure to doses of 1 and 10 Mrad(Si), respectively, under floating bias conditions, which are different from worst case conditions. For n-channel transistors the corresponding values are -0.1 and -0.2 V. The additional bottom and sidewall B⁺ ion implants with a dose of 2×10¹³ cm^-2 are found to be effective to prevent leakage current along the n-channel transistor bottom and sidewalls. SOI/CMOS ring oscillators present a 40% higher speed in comparison with the same bulk CMOS devices and continued stable operation under a supply voltage of 3-5.5 V, for gamma irradiation up to 10 Mrad(Si), and an operating temperature ranging from 77 to 400 K     

CMOS运算放大器电路的辐照损伤分析

通过分析P沟差分对输入CMOS运放电路内部单管特性，各节点电流，电压及运放整体电路在电离辐射环境中损伤特性的变化，探讨了引起运放电特性退化的主要原因，结果显示，由于差分对PMOSFET输出特性Ids-Vds的不对称，在辐照中引起的镜像恒流源的不匹配，是导致运放电参数发生剧变的根本原因，对CMOS运放电路来说，电路结构的匹配及MOSFET单管I－V持性的优劣，是决定运放抗辐射能力的关键。     

The Effects of Gamma Radiation on Glass Coated Silicon Transistors

It has previously been found that semiconductor devices employing various gas encapsulation techniques exhibited significant alterations of their electrical responses under gamma and neutron exposure. Since the neutron bombardment produces bulk or volume damage, the device surface environment has little effect on the neutron induced changes. It has been observed that gamma exposures at doses well below the threshold for permanent damage have caused changes in several electrical characteristics of transistors and diodes which may be described as of surface origin. The parameters exhibiting significant change are the transistor ICBO and the reverse biased diode leakage current. This paper will describe the results of experiments performed to study the effects of exposure to gamma radiation on selected silicon transistors when coated with a low temperature melting glass. The surface sensitive parameters of the coated transistors degraded to a much lesser extent than observed for the gas encapsulated units, indicating a more favorable surface environment to minimize the effect of gamma radiation. Comparison of the glass coated transistors with devices employing a planar structure incorporating a silicon-oxide coating on the device material surface yielded comparable results. The results of these experiments are consistent with the model proposed to explain this effect and its various ramifications.     

Surface Effects of Radiation on Transistors

Surface effects caused by ionizing radiation have been found to result in serious parameter changes in certain transistors. These effects include large increases in leakage current, changes in gain, and increases in noise. Studies have been made of the effects of dose, dose rate, bias, transistor environment, and surface protection, in addition to the phenomena of recovery and memory. The greatest changes occur when bias and radiation are applied simultaneously to a gas-encapsulated silicon transistor with unprotected surfaces. Most of these effects can be qualitatively explained through the use of a simple model of the process. Radiation ionizes the encapsulating gas, and the resulting ions and electrons are directed to transistor surfaces by electric fields at the junction surfaces and between the transistor and its can. Inversion layers are produced at the surface which grossly change certain transistor parameters. The great variability among devices of the same type suggests that the gas ions interact with the surface by imparting charge to surface contaminants. Detailed investigation of the influence of electric fields between a transistor structure and its can have been carried out on special gas-encapsulated mesa and planar transistors which are electrically insulated from their cans. Results indicate that inversion layers on both collector and base are affecting ICBO. while, as would be expected, gain is altered principally by an inversion layer on the base. In the gasencapsulated planar devices the effect of can bias on ICBO is greatly reduced and its effect on gain is practically zero.     

Two-dimensional analysis of a negative differential conductance gate transistor as a THz emitter

We investigate plasma modes in a transistor including a negative differential conductance in the gate.The analytical results show that the plasma wave generation is substantially influenced by the lateral direction (width of the transistor),gate leakage current and viscosity.The injection from the gate (opposed to the gate leakage current) can improve the plasma oscillations and their amplitude with respect to ordinary transistors.We also estimate,which to our best knowledge has been derived for the first time,the total power emitted by the transistor and the emitted pattern which qualitatively gives reasonable agreement with the experimental data.The results show that the radiated power depends on various parameters such as drift velocity,momentum relaxation time,gate leakage current and especially the lateral direction.A negative gate current enhances the power while the gate leakage current decreases the power.