High temperature gallium phosphide rectifiers

Development of high reverse breakdown voltage and low forward voltage drop stability in high power Schottky GaP rectifier for high temperature application is reported

Power transistor switching characterization

The switching properties of power transistors are investigated. The devices studied were housed in IO-3 cases and were of an n(+)-p-n(-)-n(+) vertical dopant structure. The effects of the magnitude of the reverse-base current and temperature on the reverse-bias second breakdown characteristics are discussed. Brief discussions of device degradation due to second breakdown and of a constant voltage turn-off circuit are included. A description of a vacuum tube voltage clamp circuit which reduces clamped collector voltage overshoot is given

A model based DC analysis of SiPM breakdown voltages

A new method to determine the breakdown voltage of SiPMs is presented. It is backed up by a DC model which describes the breakdown phenomenon by distinct avalanche turn-on ($V_{01}$) and turn off ($V_{10}$) voltages. It is shown that $V_{01}$ is related to the 'breakdown voltage' that previous DC methods derive from simple reverse current-voltage measurements, while $V_{10}$ is the 'real' breakdown voltage commonly obtained from complex gain-voltage measurements. The proposed method reveals how the microcell population distributes around $V_{01}$ and $V_{10}$. It is found that if this distribution is assumed to be normal, then both voltages and even their standard deviation can readily be extracted from current-voltage curves. Measurements are in good agreement with the theoretical model

Development of high temperature gallium phosphide rectifiers

Large area high performance, GaP rectifiers were fabricated by means of Zn diffusion into vapor phase epitaxial GaP. Devices with an active area of 0.01 sq cm typically exhibit forward voltages of 3 volts for a bias current of 1 ampere and have reverse breakdown voltages of 300 volts for temperatures from 27 C to 400 C. Typical device reverse saturation current at a reverse bias of 150 volts is less than 10 to the minus 9th power amp at 27 C and less than 0.000050 amp at 400 C

End-of-Sample Cointegration Breakdown Tests

This paper introduces tests for cointegration breakdown that may occur over a relatively short time period, such as at the end of the sample. The breakdown may be due to a shift in the cointegrating vector or due to a shift in the errors from being I(0) to being I(1). Tests are introduced based on the post-breakdown sum of squared residuals and the post-breakdown sum of squared reverse partial sums of residuals. Critical values are provided using a parametric subsampling method. The regressors in the model are taken to be arbitrary linear combinations of deterministic, stationary, and integrated random variables. The tests are asymptotically valid when the number of observations in the breakdown period, m, is fixed and finite as the total sample size, T+m, goes to infinity. The tests are asymptotically valid under weak conditions. Simulation results indicate that the tests work well in the scenarios considered. Use of the tests is illustrated by testing for interest rate parity breakdown during the Asian financial crisis of 1997.Cointegration, Least squares estimator, Model breakdown, Parameter change test, Structural change

Electrical Characterization of 4H-Silicon Carbide P-N Junction Diodes

The current conduction mechanisms of 4H-SiC p+n mesa diodes were studied using current-voltage-temperature (I-V-T), capacitance-voltage-temperature (C-V-T), deep level transient spectroscopy (DLTS), optical observations, and reverse breakdown measurements. Temperature and voltage dependencies of diffusion, recombination, and tunneling current processes are shown to be consistent with Sah-Noyce-Shockley theory. Recombination currents having an ideality factor of A=1.85-2.1 yielded an activation energy of EA=1.56 eV, whereas for ideal recombination, A=2 and EA=1.6 eV. Forward I-V curves of poor diodes dominated by tunneling and recombination processes, showing low reverse breakdown voltages of approx. 100 V, can be correlated to DLTS results which show large defect concentrations, and spectral observations indicating radiative recombination via defect sites. On the other hand, well-behaved diodes exhibited a breakdown voltage at approx. 450 V, a spectral output centered at 385 µm, and recombination-to-diffusion current ratios of 1012 - 1029 that agree with theory. C-V-T, DLTS, and reverse I-V-T data revealed several defect centers. C-V-T and reverse I-V-T measurements yielded an energy level at approx. 70 and approx. 62 meV, respectively, which is possibly attributable to nitrogen donor levels. Reverse I-V-T and DLTS results, in approximately half of the diodes tested, yielded a second trap level at 173 ±19 and 150 ±34 meV, respectively. Approximately 20% of the well-behaved diodes tested were found to breakdown unexpectedly at reverse biases as low as 95 V. It is believed that this unexpected breakdown is due to nanopipe defects in the diodes

Non-Micropipe Dislocations in 4H-SiC Devices: Electrical Properties and Device Technology Implications

It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vectors greater than or equal to 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = 1c with no hollow core) in densities on the order of thousands per sq cm, nearly 100-fold micropipe densities. While not nearly as detrimental to SiC device performance as micropipes, it has recently been demonstrated that elementary screw dislocations somewhat degrade the reverse leakage and breakdown properties of 4H-SiC p(+)n diodes. Diodes containing elementary screw dislocations exhibited a 5% to 35% reduction in breakdown voltage, higher pre-breakdown reverse leakage current, softer reverse breakdown I-V knee, and microplasmic breakdown current filaments that were non-catastrophic as measured under high series resistance biasing. This paper details continuing experimental and theoretical investigations into the electrical properties of 4H-SiC elementary screw dislocations. The nonuniform breakdown behavior of 4H-SiC p'n junctions containing elementary screw dislocations exhibits interesting physical parallels with nonuniform breakdown phenomena previously observed in other semiconductor materials. Based upon experimentally observed dislocation-assisted breakdown, a re-assessment of well-known physical models relating power device reliability to junction breakdown has been undertaken for 4H-SiC. The potential impact of these elementary screw dislocation defects on the performance and reliability of various 4H-SiC device technologies being developed for high-power applications will be discussed

High-Field Fast-Risetime Pulse Failures in 4H- and 6H-SiC pn Junction Diodes

We report the observation of anomalous reverse breakdown behavior in moderately doped (2-3 x 10(exp 17 cm(exp -3)) small-area micropipe-free 4H- and 6H-SiC pn junction diodes. When measured with a curve tracer, the diodes consistently exhibited very low reverse leakage currents and sharp repeatable breakdown knees in the range of 140-150 V. However, when subjected to single-shot reverse bias pulses (200 ns pulsewidth, 1 ns risetime), the diodes failed catastrophically at pulse voltages of less than 100 V. We propose a possible mechanism for this anomalous reduction in pulsed breakdown voltage relative to dc breakdown voltage. This instability must be removed so that SiC high-field devices can operate with the same high reliability as silicon power devices