A Method to Evaluate the Second Breakdown Resistance of Power Transistors

A new evaluation method of forward-biased second breakdown resistance in power transistors employing a characteristic variation of current gain is presented. Predictions for second breakdown resistance in power transistor are made by monitoring the changing point of the base current at the collector-base junction under the constant voltage and constant current conditions. This characteristic phenomenon which is related to the variation of the current gain is dependent on the temperature and current density at a localized spot of the transistor. It is concluded that the time delay required to reach the changing point of the base current can be considered as a measure of the second breakdown resistance. The forward-biased second breakdown resistance can be measured without damage or degradation of the sample transistors, if the supplied power is removed before the base current reaches the changing point.     

MBE-grown vertical power-MOSFETs with 100-nm channel length

In this work we present a new approach for solving the tradeoff between breakdown capability and on state resistance for Power-MOS devices. Therefore we use a vertical transistor on an epitaxial layer. This concept allows the adjustment of the breakdown voltage due to the thickness of the epi-layer separately from the on-state resistance, which is defined by the vertical transistor. The transistor was fabricated by means of MBE, which allows very small channel length and doping control on atomistic scale. Devices with breakdown voltages between 12 V and 40 V were produced. It is also shown that the usage of local channel doping instead of homogenous doping in the switching transistor reduces the on state resistance of the device significantly.     

Design of a rugged 60 V VDMOS transistor

Vertical double diffused MOSFET (VDMOS) is an established technology for high- current power-switching applications such as automotive circuits. The most serious failure mode is destructive damage during inductive switching, resulting from avalanche breakdown of the forward-blocking junction in the presence of high current flow. Improving the ruggedness of the device is achieved by enhancing its ability to absorb inductive energy under avalanche conditions. The purpose of the paper is to explore the possibility of improving the ruggedness of VDMOS through TCAD simulations. A p⁺-strip buried underneath an n⁺-source is proposed to suppress the turn-on of the parasitic bipolar transistor. VDMOS transistors with this design modification are expected to have higher ruggedness while maintaining its superior figure-of-merit.     

Breakdown of avalanche critical behaviour in polycrystalline plasticity

Acoustic emission experiments on creeping ice as well as numerical simulations argue for a self-organization of collective dislocation dynamics during plastic deformation of single crystals into a scale-free pattern of dislocation avalanches characterized by intermittency, power-law distributions of avalanche sizes, complex space-time correlations and aftershock triggering. Here, we address the question of whether such scale-free, close-to-critical dislocation dynamics will still apply to polycrystals. We show that polycrystalline plasticity is also characterized by intermittency and dislocation avalanches. However, grain boundaries hinder the propagation of avalanches, as revealed by a finite (grain)-size effect on avalanche size distributions. We propose that the restraint of large avalanches builds up internal stresses that push temporally the dynamical system into a supercritical state, off the scale-invariant critical regime, and trigger secondary avalanches in neighbouring grains. This modifies the statistical properties of the avalanche population. The results might also bring into question the classical ways of modelling plasticity in polycrystalline materials, based on homogenization procedures.     

Single-photon detection beyond 1 µm: performance of commercially available InGaAs/lnP detectors

Commercially available InGaAs/lnP avalanche photodiodes, designed for optical receivers and range finders, can be operated biased above the breakdown voltage, achieving single-photon sensitivity. We describe in detail how to select the device for photon-counting applications among commercial samples. Because of the high dark-counting rate the detector must be cooled to below 100 K and operated in a gated mode. We achieved a noise equivalent power of 3 × 10(-16) W/Hz(1/2) to a 1.55-μm wavelength and a time resolution well below 1 ns with a best value of 200-ps FWHM. Finally we compare these figures with the performance of state-of-the-art detectors in the near IR, and we highlight the potentials of properly designed InGaAs/lnP avalanche photodiodes in single-photon detection.     

Influence of traps on avalanche triggering during breakdown of gallium phosphide p-n junctions

Deep centers are found to strongly influence the statistical delay of microplasma breakdown in gallium phosphide red LEDs. It is postulated that this effect is caused by Shockley electrons triggering an avalanche or by subthreshold mechanisms of impact ionization. It is shown that the statistical delay in the microplasma breakdown can be used to determine the parameters of the deep centers if the charge state of the deep centers is varied by reducing the p-n junction voltage. Pis’ma Zh. Tekh. Fiz. 25, 9–13 (March 12, 1999)     

RTD振荡特性的模拟与研究

为解决共振隧穿二极管(RTD)振荡功率的提高受到稳定性限制的问题,利用高级设计系统(ADS)电路仿真,研究了RTD分别与RLC(电阻、电容、电感)、HEMT(高电子迁移率晶体管)及HBT(异质结双极晶体管)构成的大信号振荡电路,分析了其负阻、双稳特性产生振荡的机理,探索了RTD的连接器件对RTD特性的调制作用.研究表明,振荡电压(或电流)的峰值与谷值之差越大,输出电压(或电流)的振荡幅度就越大,且比单纯增大RTD结面积来增大输出功率的做法有更好的稳定性,据此有望解决功率受限的问题;RTD连接的器件对R TD特性的调制作用与连接方式有关,通过改变连接方式可以扩大RTD在射频收发系统中的应用.     

Operational life testing of power transistors switching unclamped inductive loads

This paper describes three types of high voltage power transistors that are in widespread use in the electronics industry today, and their susceptibility to reverse-biased second breakdown while switching unclamped inductive loads. It provides a brief explanation of the phenomenon of second breakdown in transistors under both forward-biased and reverse-biased conditions. It describes a stress circuit that has been developed to incorporate switching of unclamped inductive loads as an integral part of operational life testing. A case history incorporating this technique is presented for the 2SD1739 high voltage NPN bipolar power transistor.     

A.C. electrical breakdown in thin magnesium oxide films

A systematic study of a.c. breakdown in magnesium oxide films of thickness 40–200 Å fabricated into capacitors is reported. It is found that the breakdown strength is a power function of the thickness d, varying as d^?0.23, as predicted by the theory of Forlani and Minnaja based on the ionization avalanche mechanism.     

N-channel accumulation layer MOSFET operating at 4 K

An accumulation layer n-channel MOSFET that operates at 4 K has been fabricated. Sharp hysteretic current kinks in the I–V characteristic are observed, where the transistor switches discontinuously between two well defined states. The kinks are modelled in terms of changes in the device potential configuration due to holes generated by avalanche breakdown in the high electric field region near pinch off. Noise measurements which elucidate the physical mechanisms causing the current kinks are presented.     

An integrated active-quenching circuit for single-photon avalanchediodes

We introduce the first integrated active quenching circuit (I-AQC) that drives an avalanche photodiode (APD) above its breakdown voltage, in order to detect single photons. Based on the I-AQC, we developed a compact and versatile photon-counting module suitable for applications in which very weak optical signals have to be detected, as for instance, photon correlation spectroscopy, luminescence measurements, and laser ranging. The prototype photon-counting module features quenching pulses up to 60 V amplitude, minimum dead time of less than 36 ns, corresponding to a saturated counting rate exceeding 25 Mcounts/s, user-controllable hold-off time, for reducing the afterpulsing effect, and nanosecond gating capability. The power dissipation is 60 mW in stand-by conditions, and the module size is less than 1 cm×2 cm     

Photon counting with passively quenched germanium avalanche

We demonstrate photon counting in germanium avalanche photodiodes biased beyond breakdown and quenched with a simple series resistance circuit. The devices show moderate (> 7%) quantum efficiency with limited afterpulsing and dark counts and subnanosecond jitter.     

Dielectric breakdown study of thin La2O3 films

The dielectric breakdown in La₂O₃ films of thickness 40–400 Å incorporated in capacitors is reported. The experimental results were analysed in the light of Forlani and Minnaja's theory of ionization avalanche breakdown. The dielectric breakdown strength was found to be a power function of thickness, varying as d^?0.66, in essential agreement with the theory of Forlani and Minnaja. Furthermore, these films are amorphous and have high breakdown fields (about 10 MV cm^?1).     

Discrimination capability of avalanche counters detecting different ionizing particles

The discrimination capability of avalanche counters to detect different ionizing particles has been studied using a ²⁵²Cf source. Pulse height, pulse-height resolution and timing properties have been measured as a function of the reduced applied voltage for parallel-plate and parallel-grid avalanche counters. At the highest applied voltages, space charge effects shift the pulse-height signal of the avalanche counter away from being linearly proportional to the stopping power of the detected particles and cause the pulse-height resolution to deteriorate. To optimize the avalanche counter capability, without loss of time resolution, it appears better to operate the detector at voltages well below the breakdown threshold. Measurements with ³²S ions are also reported.     

Thickness dependence of breakdown field in thin films

Studies of the thickness dependence of dielectric breakdown in thin films are of fundamental importance for the development of devices. Here a systematic study of the d.c. breakdown in “built-up” ionic films of barium stearate is reported in the thickness range (25–2000 Å). These films are ideally suited for such studies because of their perfect reproducibility and control of their thicknesses which are uniform and very accurately known. The breakdown strength is found to be a power dependent function of thickness as predicted by Forlani and Minnaja's theory based on an electron ionization avalanche mechanism. The films studied have recently been found to be promising for making devices.     

Optical amplification in a planar multichannel Mach-Zehnder interferometer based on metal-semiconductor-metal structures

This paper describes a new optoelectronic device—an optical transistor that provides power amplification of output visible radiation. The optical transistor is structurally based on a metallized semiconductor plate with a microchannel gap in the form of a planar Mach-Zehnder interferometer. A device of the light-light type is controlled by modulating the refractive index in one arm of the interferometer. Pis’ma Zh. Tekh. Fiz. 24, 17–21 (January 26, 1998)     

Triggering of dry snow slab avalanches: stress versus fracture mechanical approach

This paper analyses the conditions for triggering of dry snow slab avalanches. As suggested by several Authors, we assume as a basic mechanism for avalanche triggering the mode II fracture of the weak layer lying beneath the stiff snow slab, i.e. we assume the presence of super-weak zones in the basal layer. By means of a linear elastic analysis, the shear stresses in the weak layer as well as the strain energy release rate caused by an increment of the super-weak zone are evaluated. Hence we introduce a stress failure criterion as well as an energy one. It is shown that the latter criterion can be seen as an extension of the criterion firstly proposed by McClung [McClung, D.M., 1979. Shear fracture precipitated by strain softening as a mechanism of dry slab avalanche release. Journal of Geophysical Research, 84(B7), 3519-3526.] for dry snow slab avalanche release. Finally we couple the two criteria, showing that the weak layer can fail only in a min–max band of thickness.     

AlGaN solar-blind APD with low breakdown voltage

A p-i-i-n type AlGaN heterostructure avalanche photodiodes (APDs) is proposed to decrease the avalanche breakdown voltage and to realize higher gain by using high-Al-content AlGaN layer as multiplication layer and low-Al-content AlGaN layer as absorption layer. The calculated results show that the designed APD can significantly reduce the breakdown voltage by almost 30%, and about sevenfold increase of maximum gain compared to the conventional AlGaN APD. The noise in designed APD is also less than that in conventional APD due to its low dark current at the breakdown voltage point. Moreover, the one-dimensional (1D) dual-periodic photonic crystal (PC) with anti-reflection coating filter is designed to achieve the solar-blind characteristic and cutoff wavelength of 282 nm is obtained.     

GaAs three-terminal double delta-doped triangular barrier switch prepared by molecular beam epitaxy

A novel S-shaped negative differential resistance (NDR) switching device, prepared by molecular beam epitaxy (MBE), has been successfully developed in a GaAs double delta-doped triangular barrier (TB) structure. All symmetrical S-shaped NDR characteristics, either unidirectional or bidirectional bistability phenomena, are observed experimentally. The bidirectional current-voltage (I–V) characteristics exhibit a new type of NDR caused by an avalanche multiplication process in the reverse-biased base-collector region and by barrier redistribution. Under a base current injection with respect to the cathode, the device behaves as a conventional transistor with a current gain of 1.2 at room temperature. Experimentally, electrical results can be easily understood by an equivalent circuit and a proposed model. In addition, a new optoelectronic switching device is also proposed which may have the potential for bidirectional wavelength emission. On the basis of the first utilization of a double delta-doped TB structure, a conceptual understanding of such a set of results enhances our understanding of the physics of double delta-doped TB devices in general.