Low capacitance ESD protection circuits for GaAs RF ICs

We present a novel electrostatic discharge (ESD) protection circuit for GaAs radio frequency (RF) integrated circuits (ICs), which are targeted for 10 Gb/s fiber-optic communication applications. The robustness, parasitic impedance, and loading effect of the new ESD protection circuit are studied and compared with the conventional diode-based ESD protection technique. Two versions of this type of ESD protection circuit were fabricated with a 60-GHz InGaP heterojunction bipolar transistor (HBT) technology. These two circuits can withstand, respectively, 2700 and 5000 V human body model (HBM) ESD stress and provide a similar level of ESD protection to RF ICs. The corresponding impedances of the off state are represented by an equivalent shunt capacitance and shunt resistance of 0.22 pF and 500 Ω, and 0.5 pF and 250 Ω, at 10 GHz. This ESD protection circuit can protect the 10 Gb/s RF ICs against much higher level ESD stress than conventional diode-based ESD protection circuits even with smaller size.     

Preparation of PVOH coatings with graphene nanoplatelets for electrostatic discharge protective packaging

This study investigated the use of graphene nanoplatelets (GNP) as a conductive filler for electrostatic discharge (ESD) protective packaging. Various weight concentrations of GNP were mixed and sonicated with polyvinyl alcohol (PVOH). The resulting polymer solution was applied as a coating to corrugated board in order to form an ESD packaging. Surface resistivity, mechanical strength and coating adhesion were then measured. The study found that the electrical percolation threshold of the PVOH/GNP coating is 9–13wt% GNP. GNP incorporated PVOH coatings with surface resistivity of 10³–10⁸ Ω/sq. generally meet all of ESD packaging requirements. The humidity strongly affects the surface resistivity of the coatings below the percolation threshold, but the change of the surface resistivity with humidity is less significant above the percolation threshold.     

Analysis of electrostatic discharge suppressors with ultra-low capacitance used for IC protection

The TDMM was successfully used to analyze the capacitance, the electric field, and the ESD current of an ESD suppressor. The obtained capacitance was also validated by measurement data. It is found that the maximum electric fields in the air gap between two discharge electrodes for the air gap width of 5–50 μm are much higher than the threshold electric field for air breakdown. A maximum ESD current of 4.7 mA was obtained during an ESD event, which may be sufficient to cause a malfunction in a high sensitivity integrated circuit.     

Amplified luminescence in InGaAs/AlGaAs laser diode arrays at high pump levels

The development of amplified luminescence fluxes in powerful InGaAs/AlGaAs laser diode arrays (lasing wavelength 940–960 nm) has been studied experimentally and theoretically at pump levels above the threshold value. Flux density values for amplified luminescence propagation along (1.88⋅10⁹ W/m²) and across (1.21⋅10⁹ W/m²) the laser diode array cavity axis have been evaluated for the threshold pump level at room temperature (293 K). The contribution of the recombination rate induced by the amplified luminescence to the threshold current generation of the laser diode array reaches 7%. It has been shown that the amplified luminescence flux density is increased by 49% as the pump level rises from one to three threshold values.     

Entrance surface dose in cerebral interventional radiology procedures

During interventional radiology procedures patients receive doses which exceed thresholds for non-stochastic effects on the skin, such as erythema (2 Gy) and epilation (3 Gy), so the entrance surface dose imparted during these proceedings should be monitored. The aim of this work was to determine the entrance surface dose (ESD) in patients who undergo diagnostic or therapeutic procedures at the Instituto Nacional de Neurología y Neurocirugía (INNN). The procedures were performed using two systems for neuroradiology, an Axiom Artis and an Artis Zeego from Siemens. The ESD was measured, for diagnostic and therapeutic procedures, using 15 × 15 cm² of Gafchromic XR-RV3 film and/or 25 TLD-100 chips that were attached in a holder of 15 × 15 cm² in the posteroanterior and left and right lateral positions during all the procedures. The results show that the maximum ESD measured was lower than 1 Gy for the nine diagnostic procedures evaluated whereas four of the ten therapeutic procedures were greater than 2 Gy in at least one position. Seven patients were monitored, three of which have presented epilation and one erythema.     

Reduction of the contact resistance in copper phthalocyanine thin film transistor with UV/ozone treated Au electrodes

Bottom-contact (BC) copper phthalocyanine (CuPc) thin film transistor with UV/ozone treated Au as a source/drain electrode was fabricated and the contact resistance was estimated from the transmission line method (TLM). Comparing the properties of OTFT with untreated Au electrode, the performance of the BC CuPc-TFT with the UV/ozone treated Au electrodes was significantly improved: saturation mobility increased from 4.69 × 10⁻³ to 2.37 × 10⁻² cm²/V s, threshold voltage reduced from −29.1 to −6.4 V, and threshold swing varied from 5.08 to 2.25 V/decade. The contact resistance of the device with UV/ozone treated Au electrodes was nearly 20 times smaller than that of the device with untreated Au electrodes at the gate voltage of −20 V. This result indicated that using the UV/ozone treated Au electrode is an effective method to reduce the contact resistance. The present BC configuration with UV/ozone treated Au electrodes could be a significant step towards the commercialization of OTFT technology.     

Detection of nanoscale ESD effect on GMR head signal using the wavelet transform technique: HBM and CDM cases

An electrical signal anomaly is an undesired signal and is difficult to detect by a commercial instrument due to its short duration and unpredictable fault on a signal. Since a GMR recording head is a stack of nanometer thick multilayers, in particular, a magnetic layer and conductor layers, for magnetic insulating spacers, it is very sensitive to electron movements. Visible damage is understandable and protectable but latent failure cannot be measured. It is possibly observed by using frequency-domain apparatus but certainly it is not real-time detection. Therefore, in order to detect a latent failure head affected by ESD in the time domain, current conventional instruments are ineffective. In this study, the wavelet transform technique using the 4th order Daubechies is proposed to detect the glitches on a magnetic recording head signal in the time domain. It is found that the glitches occur when the ESD level of the charged device model (CDM) and human body model (HBM) on giant magnetoresistive (GMR) heads are in ranges of 6–15 V and 40–120 V, respectively. The electrical test parameters and scanning electron microscope (SEM) photo of the recording heads show no visible change in reader sensor. To ensure the results, the GMR damage is observed by SEM when the CDM-ESD and HBM-ESD are 10 V and 130 V, respectively. The glitches in the magnetic response signal of the GMR head are found to increase when the ESD level is increased. Thus, the Daubechies wavelet transform technique can be a novel approach to detect the pre-degradation of a GMR head due to an ESD effect.     

Field emission behavior of cuboid zinc oxide nanorods on zinc-filled porous silicon

Single-crystalline zinc oxide (ZnO) nanorods with cuboid morphology have been prepared on the zinc-filled porous silicon substrate using a vapor phase transport method. Field-emission measurements showed that the turn-on field and threshold field of the cuboid ZnO nanorods film were about 3.2 and 8.2 V/μm respectively. From the emitter surface, a homogeneous emission image was observed with emission site density (ESD) of ∼10⁴ cm⁻². The better emission uniformity and the high ESD may be attributed to a large number of ZnO nanocrystallites as emitter on the surface of the nanorod end contributing to emission.     

Evaluation of ESD hardness of fingerprint sensor LSIs

We evaluated the electrostatic discharge (ESD) hardness of capacitive fingerprint sensor large scaled integrated circuits (LSIs) with two kinds of ESD test methods.We used three kinds of fingerprint sensor LSIs, i.e., a conventional planar sensor LSI, a sensor LSI with a grounded wall (GND wall) structure where each sensor plate was surrounded by a lattice-like wall, and a sensor where some of the sensor plates had been replaced with GNDs. In human body model (HBM)-based contact discharge tests, the sensor LSI with the GND wall structure and the one with the GNDs demonstrated a high ESD hardness compared with the planar sensor LSI. An air discharge test was also carried out in accordance with IEC61000-4-2 specifications because other ESD tests cannot be used to estimate over ±8 kV. The ESD hardness of the GND wall structure was ±20 kV, whereas that of the other sensor with the GND structure was below ±12 kV. It was evident from our findings that the ESD hardness of sensor LSIs obviously depends on the number of GNDs in the sensor region, their arrangement, and the GND structure, and that the sensor LSI with the GND wall had the highest ESD hardness.     

Low threshold current density, low resistance oxide-confined VCSEL fabricated by a dielectric-free approach

We present the fabrication process and experimental results of 850-nm oxide-confined vertical cavity surface emitting lasers (VCSELs) fabricated by using dielectric-free approach. The threshold current of 0.4 mA, which corresponds to the threshold current density of 0.5 kA/cm², differential resistance of 76 Ω, and maximum output power of more than 5 mW are achieved for the dielectric-free VCSEL with a square oxide aperture size of 9 μm at room temperature (RT). L–I–V characteristics of the dielectric-free VCSEL are compared with those of conventional VCSEL with the similar aperture size, which indicates the way to realize low-cost, low-power consumption VCSELs with extremely simple process. Preliminary study of the temperature-dependent L–I characteristics and modulation response of the dielectric-free VCSEL are also presented.     

All-optical ion generation for ion trap loading

We have investigated the all-optical generation of ions by photo-ionisation of atoms generated by pulsed laser ablation. A direct comparison between a resistively heated oven source and pulsed laser ablation is reported. Pulsed laser ablation with 10 ns Nd:YAG laser pulses is shown to produce large calcium flux, corresponding to atomic beams produced with oven temperatures greater than 650 K. For an equivalent atomic flux, pulsed laser ablation is shown to produce a thermal load more than one order of magnitude smaller than the oven source. The atomic beam distributions obey Maxwell–Boltzmann statistics with most probable speeds corresponding to temperatures greater than 2200 K. Below a threshold pulse fluence between 280 mJ/cm² and 330 mJ/cm², the atomic beam is composed exclusively of ground-state atoms. For higher fluences ions and excited atoms are generated.     

60Co γ射线辐射对AlGaN/GaN HEMT器件的影响

采用⁶⁰Co γ射线辐射源对非钝化保护的AlGaN/GaN高电子迁移率晶体管(HEMT)器件进行了1 Mrad(Si)的总剂量辐射,实验发现辐射累积剂量越大,器件尺寸越小,器件饱和漏电流和跨导下降越明显,同时辐射后器件栅泄漏电流明显增大,而阈值电压变化很小. 对辐射前后器件的沟道串联电阻和阈值电压变化的分析表明,辐射感生表面态负电荷的产生是造成AlGaN/GaN HEMT器件电特性退化的主要原因之一. 关键词： AlGaN/GaN HEMT器件 γ射线辐射 表面态     

Ohmic contact and space-charge-limited current in molybdenum oxide modified devices

The effect of indium-tin oxide (ITO) surface treatment on hole injection of devices with molybdenum oxide (MoO₃) as a buffer layer on ITO was studied. The Ohmic contact is formed at the metal/organic interface due to high work function of MoO₃. Hence, the current is due to space charge limited when ITO is positively biased. The hole mobility of N, N′-bis-(1-napthyl)-N, N′-diphenyl-1, 1′biphenyl-4, 4′-diamine (NPB) at various thicknesses (100–400 nm) has been estimated by using space-charge-limited current measurements. The hole mobility of NPB, 1.09×10⁻⁵ cm²/V s at 100 nm is smaller than the value of 1.52×10⁻⁴ cm²/V s at 400 nm at 0.8 MV/cm, which is caused by the interfacial trap states restricted by the surface interaction. The mobility is hardly changed with NPB thickness for the effect of interfacial trap states on mobility which can be negligible when the thickness is more than 300 nm.     

Active region design of a terahertz GaN/ Al0.15Ga0.85N quantum cascade laser

We propose the idea of developing THz quantum cascade lasers (QCLs) with GaN-based quantum well (QW) structures with significant advantages over the currently demonstrated THz lasers in the GaAs-based material system. While the ultrafast longitudinal optical (LO) phonon scattering in AlGaN/GaN QWs can be used for the rapid depopulation of the lower laser state, the large LO-phonon energy (∼90 meV) can effectively reduce the thermal population of the lasing states at higher temperatures. Our analysis of one particular structure has shown that a relatively low threshold current density of 832 A/cm² can provide a threshold optical gain of 50/cm at room temperature. We have also found that the characteristic temperature in this structure is as high as 136 K.     

Controlling the electrostatic discharge ignition sensitivity of composite energetic materials using carbon nanotube additives

Powder energetic materials are highly sensitive to electrostatic discharge (ESD) ignition. This study shows that small concentrations of carbon nanotubes (CNT) added to the highly reactive mixture of aluminum and copper oxide (Al + CuO) significantly reduces ESD ignition sensitivity. CNT act as a conduit for electric energy, bypassing energy buildup and desensitizing the mixture to ESD ignition. The lowest CNT concentration needed to desensitize ignition is 3.8 vol.% corresponding to percolation corresponding to an electrical conductivity of 0.04 S/cm. Conversely, added CNT increased Al + CuO thermal ignition sensitivity to a hot wire igniter.     

A mathematical expression for air ESD current waveform using BP neural network

A curve-fitting method based on backpropagation (BP) neural network (NN) is proposed for fitting electrostatic discharge (ESD) current waveforms and giving the corresponding expressions in order to analyze the characteristics of ESD and calculate the ESD electromagnetic pulse radiation field. According to IEC61000-4-2, this method is used to fit the ideal contact current waveform of human-metal ESD to obtain the mathematical expression. The waveform parameters of the fitting curve meet the requirements of the IEC61000-4-2. By fitting the measured air ESD current waveform at 4 kV discharge, the mathematical expression is obtained. This paper proposes the mathematical expression for arbitrary curves and analyzes the factors affecting the effects of curve-fitting.     

Human-to-metal electrostatic discharge current measurements – Notes on the ESD current waveform

The Electrostatic Discharge (ESD) phenomenon has been described through the IEC 61000-4-2. ESD current parameters' values, have been set in this Standard. The theoretical ESD current waveform defined in this standard, describing the conventional Contact discharge mode, needs to be re-evaluated on the basis of accurate experimental data. Even though the standard deals with commercial ESD generators, its goal is to simulate the natural phenomenon as good as possible. More and accurate data may contribute to the better simulation of the natural phenomenon. New values and better comprehension of the phenomenon demand new measurements based on high end measuring equipment. Such works and publications have been carried out the past years. Yet, the need to systematize and integrate this work remains. Larger and trust-worthy series of measurements need to be carried out and presented clearly.This paper deals with new ESD-current data, taken with broadband equipment. New and more detailed measurements like these, were never before taken at such a large number of individuals. The goal of this work is that the data acquired can serve as a basis for re-evaluating the conventional approach of the scientific community to the ESD event.In this paper, using a broadband measuring system, new parameters' values are measured and relations are presented, following standard statistical procedures. The results, which occur from measurements carried out on tenths of human individuals, are questioning the Standard in many points. A new way of approaching the standardization of the ESD current is proposed, as the excuse of the poor measuring equipment that sets barriers on the measuring accuracy, does not apply any more. The charging voltages of 500 V and 1000 V were also examined since such range of voltages are often met at ESD events and they are considered very harmful.     

Influence of thermal treatment on the performance of copper phthalocyanine thin-film transistors

Organic thin-film transistors (OTFTs) with bottom-gate and bottom-contact configuration based on copper phthalocyanines (CuPc) as active layer were fabricated. The performance of CuPc OTFTs was studied before and after thermal treatment on CuPc layer. The values of the threshold voltage before and after thermal treatment are −6.3 and −5.7 V, respectively. The field-effect mobility values in saturation regime of CuPc thin-film transistors before and after thermal treatment are 0.014 cm²/Vs and 0.0068 cm²/Vs, respectively. The experimental results indicate that there is a heavy decay on the mobility of CuPc based OTFTs mostly due to the crystalline morphology change induced by the thermal treatment, and absolute value of the threshold voltage after thermal treatment decreases with the decrease of the CuPc film thickness and the roughness.     

Gamma-ray irradiation effects on distributed-feedback laser diodes

Since laser diodes are increasingly used in harsh environments, the effect of irradiation on their performance attracts a lot of attention. We perform experiments for investigating the irradiation effects on laser diodes with distributed feedback operating at 1550 nm output wavelength with 2 mW output power. The radiation source is Co⁶⁰ gamma ray with a dose rate of 0.5 Gy/s and the dose range within 10² – 8 ∙ 10³ Gy. We study experimentally the threshold current, slope efficiency, and spectrum versus the variations in total dose. The results show that the threshold current increases exponentially and the slope efficiency decreases with increase in total dose. In addition, some sharp peaks appear in the spectrum at small driving current, and the spectrum broadens when the driving current increases and, meanwhile, the peak blue shift is observed. The spectrum can be recovered after annealing for 12 hours and when a greater driving current is applied.     

入射电子能量对低密度聚乙烯深层充电特性的影响

高能带电粒子与航天器介质材料相互作用引起的深层带电现象, 一直是威胁航天器安全运行的重要因素之一. 考虑入射电子在介质中的电荷沉积、能量沉积分布以及介质中的非线性暗电导和辐射诱导电导, 建立了介质深层充电的单极性电荷输运物理模型. 通过求解电荷连续性方程和泊松方程, 可以得出不同能量 (0.1–0.5 MeV) 电子辐射下, 低密度聚乙烯 (厚度为1 mm) 介质中的电荷输运特性. 计算结果表明, 不同能量的电子辐射下, 介质充电达到平衡时, 最大电场随入射能量的增加而减小; 同一能量辐射下, 最大电场随束流密度的增大而增加. 入射电子能量较低时 (≤ 0.3 MeV) , 最大电场随束流密度的变化趋势基本相同. 具体表现为: 当束流密度大于3× 10^-9 A/m²时, 最大场强超过击穿阈值2×10⁷ V/m, 发生静电放电 (ESD) 的可能性较大. 随着入射电子能量的增加, 发生静电放电 (ESD) 的临界束流密度增大, 在能量为0.4 MeV时, 临界束流密度为6×10^-8 A/m². 当能量大于等于0.5 MeV时, 在束流密度为10^-9–10^-6 A/m²的范围内, 均不会发生静电放电 (ESD) . 该物理模型对于深入研究深层充放电效应、评估航天器在空间环境下 深层带电程度及防护设计具有重要的意义. 关键词： 高能电子辐射 低密度聚乙烯(LDPE) 介质深层充电 电导特性