Strong Impact Ionization Research Articles

Simulation study of single-event burnout in hardened GaN MISFET

This paper presents simulation results of a single event burnout (SEB), for a hardened GaN metal-insulator-semiconductor field-effect transistor (MISFET), employing a dual channel p-type buried layer structure (DCP-MISFET). After irradiance with a heavy ion beam, the peak electric field around the gate channel was observed to move towards the drain channel. In addition, the electrons released by the bombardment of heavy ions were also seen to move towards the drain channel, resulting in strong impact ionization at the drain terminal. Compared to the conventional MISFET with field plates (FPC-MISFET), the distribution of electric field and the impact ionization, after heavy ion's exposure around the drain channel are improved in the GaN DCP-MISFET. Because of the second channel, the electrons induced by the heavy ion beam, change their direction. The proposed DCP-MISFET can achieve a better SEB performance than FPC-MISFET. with a heavy ion beam having the linear energy transfer (LET) value of 0.6 pC/μm at x = 7.5 μm striking vertically, the SEB threshold voltages that were obtained in FPC-MISFET and DCP-MISFET were 520 and 920 V, respectively.

Single Event Burnout Hardening Technique for High-Voltage p-i-n Diodes With Field Limiting Rings Termination Structure

High-voltage p-i-n diodes for space applications are sensitive to single event burnout (SEB), which may cause the failure of the entire electronic system. This article describes the SEB failure mechanism of high-voltage p-i-n diodes with field limiting rings (FLRs) termination structure, based on the electro-thermal coupled transient simulation model in the Sentaurus TCAD simulator. The simulation results show that the catastrophic failures result from the intense local heating at the edge of the main junction, because the high electric field strength at this region induces strong impact ionization of the charge carriers. The strike at the edge of the main junction shows the strongest sensitivity to SEB since the energetic particle-induced carriers are deposited exactly at the high electric field region. Then, a novel SEB hardening technique of localized carrier lifetime control at the edge of the main junction region is proposed based on the analysis on the failure mechanism. Our simulation results demonstrate that the reduction of the localized carrier lifetime can alleviate the peak electric field and reduce the local heat accumulation, thereby improving the SEB performance of high-voltage p-i-n diodes.

Research of single-event burnout and hardened GaN MISFET with embedded PN junction

This paper describes a single-event burnout (SEB) simulation for a conventional GaN MISFET field plate (FPC-MISFET) and a MISFET with an embedded pn junction (EJ-MISFET). The SEB triggering mechanism is affected by impact ionization. The electrons, which are induced by heavy ion exposure, can rapidly move to the drain, which leads to strong impact ionization around the drain. Compared to the FPC-MISFET, both the peak electric field and the impact ionization around the drain are reduced in the GaN MISFET with the embedded pn junction. The proposed EJ-MISFET also shows improved SEB performance. For a heavy ion, with a linear energy transfer (LET) of 0.6 pC/μm (hitting the devices) vertically, the SEB threshold voltages for the FPC-MISFET and EJ-MISFET are 520 and 760 V, respectively.

Safe Operating Area of GaAs HBTs Based on Sub-Nanosecond Pulse Characteristics

Using a novel sub-nanosecond pulse current-voltage measurement technique, InGaP/GaAs heterojunction bipolar transistors (HBTs) were shown to survive strong impact ionization and to have a much larger safe operating area (SOA) than previously measured or predicted. As the result, an empirical model for impact ionization with both voltage and current dependence was extracted and added to a commercially available HBT model. The modified model could predict the HBT characteristics across the enlarged SOA, as well as the performance of ultra-wideband pulse generators and the ruggedness of continuous wave Class-C power amplifiers.

Analysis of operation mechanism of semi-insulating GaAs photoconductive semiconductor switches

This paper reports that the quenched-domain mode of luminous charge domain has been observed in semi-insulating (SI) GaAs photoconductive semiconductor switches (PCSSs) and the typical characteristics of lock-on effect have been explained based on the model of luminous charge domain. It is shown that the domain is formed by photogenerated carriers and the quenched domain is due to the interaction of the circuit self-excitation and transferred-electron oscillation in the bulk of switch. During the transit of the domain, the bias electric field (larger than Gunn threshold) across the switch is modulated by the ac electric field, when the instantaneous bias electric field is swinging below the sustaining field (the minimum electric field required to support the domain), and then the quenched-domain mode is obtained. When PCSSs operate in nonlinear mode, the ultrahigh electric field of domain induced by photogenerated carriers leads to strong impact ionization accompanied by electron-hole recombination radiation in the switch. Therefore new avalanche domains can be nucleated uninterruptedly by the carriers generated by absorption of recombination radiation which causes the effective carrier velocities to be larger than the saturation velocity. Lock-on field resulted from the length proportional number of domains and steadfast electric fields inside and outside the domains, and the recovery of lock-on effect is caused by the domain quenching. The calculations agree with the experimental results, and the analysis also indicates that SI-GaAs PCSS is a photoactivated charge domain device.

Monte Carlo Modeling of Electron Scattering in Nonconductive Specimens

Very low energy electrons in a solid should behave like Bloch electrons and will interact with perturbations of the atomic lattice, that is, with phonons. So we use the acoustic phonon scattering for replacing the elastic binary encounter approximation of the Mott scattering for electrons with low energies E < 100 eV. For ballistic electrons (1 eV < E < Eg) and higher energies up to 1 keV we determined the acoustic phonon scattering and the impact ionization rate by means of the "backscattering-versus-range" proof and respective eta(E0) - R(E0) diagrams. Electron trajectories demonstrate the relatively short range of primary electrons (PE) with energies E > 50 eV due to strong impact ionization losses (cascading) and the much greater range of secondary electrons (SE) with E < 50 eV, finally as a consequence of less effective phonon losses. The field-dependent transport parameters allow us to model the self-consistent charge transport and charging-up of insulating SiO2 layers during electron bombardment maintained by the current components of primary electrons jPE, secondary electrons jSE, and associated ballistic holes jBH, as well as by Fowler-Nordheim field injection jFN from the substrate. The resulting distributions of currents j(x, t), charges p(x, t), electric fields F(x, t), and the potential V(x, t) across the dielectric layer explain the phenomena of field-enhanced and field-blocked secondary electron emission with rates delta >or<or=1.

Investigation and modeling of impact ionization in HEMTs for DC and RF operating conditions

By performing Monte Carlo simulations of InAlAs/InGaAs high-electron-mobility transistors (HEMTs), we have reproduced the measured DC, RF, and on-state breakdown characteristics of a real device. Our calculations reveal for open-channel conditions the occurrence of impact ionization not only in the channel but also in the cap layer of our device. The necessary conditions for this phenomenon are discussed. Furthermore, the dynamic of breakdown is studied by calculating the frequency-dependent two-port parameters for operating the HEMT under high-ionization conditions. A significant frequency dispersion of the extracted small-signal elements is obtained in the conventional equivalent circuit model of the FET. In order to eliminate this dispersion, we propose a new small-signal equivalent circuit model which includes strong impact ionization effects on the microwave performance and overcomes the limitations of previous models.

Emergence of a multidomain regime and spatiotemporal chaos in Gunn diodes under impact ionization conditions

Nonlinear spatiotemporal dynamics of carrier densities in Gunn diodes under impact ionization conditions is numerically investigated using a set of model partial differential equations. Numerical results show that a multidomain regime emerges as a result of the decrease in domain size caused by impact ionization, and that the spatiotemporal evolution of the domains becomes chaotic in the presence of strong impact ionization.

TYPE S BULK NEGATIVE DIFFERENTIAL CONDUCTIVITY IN n-InSb

The relationship between type S and type N (Gunn effect) bulk negative differential conductivity (BNDC) is shown in n-InSb at 77 K and atmospheric pressure. The results of conduction measurements and of radiative recombination measurements, both in time and space, shown that an S-BNDC is created in the wake of a propagating high-field domain and that the large currents associated with the S-BNDC are caused by strong impact ionization in the domain.

Anomalous Hall Effect in n-Type InSb in Pulsed High Electric Fields

Experimental studies of the Hall effect in n-type InSb at 77°K have been made in weak transverse magnetic fields (H\\lesssim300 oersteds) for electric fields in the region of the onset of impact ionization. It is known that the Hall coefficient, RH decreases sharply when electron-hole pairs are produced by impact ionization. The observed RH, however, decreases before strong impact ionization sets in and exhibits a minimum. If the magnetic field is sufficiently weak (H\\lesssim100 oersteds), the sign of RH changes from negative (normal for n-type InSb) to positive, with increasing electric field. The anomalous behavior of RH disappears with increasing magnetic field. It is shown experimentally that the observed anomalous Hall effect is related to the transverse and longitudinal asymmetries of potential caused by hole-injection from the anode.