Jonathan A. Kulisek

Carrier-Removal Comparison (n/p) and Functional Testing of Si and SiC Power Diodes

Commercial Si and 4H-SiC Schottky barrier power diodes were irradiated in the mixed neutron and gamma-ray radiation field of The Ohio State University research reactor (OSURR). The forward I-V characteristics were measured before and immediately after each successive irradiation, and the carrier-removal rates were compared, on the basis of NIEL, to a previous study, for which the same diode models were irradiated with a 203 MeV proton beam. In addition, a number of SiC Schottky barrier diodes were also irradiated in the OSURR and subsequently functionally tested in half-wave rectifier circuits, for which the voltage and current waveforms in the circuit were recorded. The results from the functional testing of these half-wave rectifier circuits were analyzed using results from I-V characterization, PSpice simulations, and an analytical formulation.

The Effects of Neutron Radiation on the Electrical Properties of Si and SiC Schottky Power Diodes

In support of future NASA space missions requiring radiation hard semiconductors, commercial Schottky power diodes made of Si and SiC were subjected to various neutron fluences at the Ohio State University Research Reactor (OSURR). I‐V measurements were taken before and after the diodes were irradiated, both in forward and reverse bias. Very little change was observed under conditions of reverse bias for the both the Si and SiC diodes, and the reverse leakage current for the SiC diodes actually decreased with increasing neutron fluence. The forward resistance for both the Si and SiC diodes increased with increasing neutron fluence.

TRIM Modeling of Displacement Damage in SiC for Monoenergetic Neutrons

Although silicon carbide is a very good semiconductor material for the fabrication of diode detectors for use as neutron power monitors in nuclear reactors, the electrical properties of the diodes may be altered because of interactions between energetic neutrons and SiC atoms. If the energy that is transferred from a neutron to an atom in a collision exceeds some threshold value, the atom will be moved from its original position, creating displacement damage. Accurately modeling displacement damage is a first step to finding ways to eliminate or decrease the amount of damage the displacements induce. The methodology that we have used to estimate the number of displacements per atom per fluence, using two codes (MCNP and TRIM) is presented in this paper, along with examples of the results of our calculations.

ANALYSIS OF DISPLACEMENT DAMAGE DOSE AND LOW ANNEALING TEMPERATURES ON THE I-V CHARACTERISTICS OF SiC SCHOTTKY DIODES USING ANOVA METHOD

Abstract Silicon carbide (SiC) is a promising semiconductor material for use in solid-state radiation detectors. SiC’s wide bandgap makes it an appropriate semiconductor for high-temperature applications. Because of the annealing process that occurs at temperatures above 150°C for SiC, SiC semiconductors may function in a radiation environment for longer periods of time at elevated temperatures than at room temperature. Unlike thermal annealing effects that can act to improve the electrical characteristics of SiC, fast neutrons create displacement damage defects in SiC Schottky diodes through scattering and thus rapidly degrade the electrical properties of the SiC diodes. We irradiated SiC Schottky diodes at the Ohio State University Research Reactor at room temperature with neutrons for displacement damage doses (Dd’s) ranging from 7.6 × 1010 to 3.8 × 1011 MeV/g. After irradiation, we annealed the diodes, at either 175 or 300°C. We measured the SiC diodes’ forward bias resistances at different steps of the experiments. To perform the experiments and study the results meaningfully, we performed a full factorial design of experiments with two factors: Dd and annealing temperature. The Dd factor had five levels of treatment, and the temperature had three levels of treatment. We did one-way and two-way analysis of variance to understand which factor is more dominant and whether or not the interaction effects are significant. It was determined that for Dd up to 2.3 × 1011 MeV/g the fractional damage recovery decreases with increasing Dd, but that Dd is not a significant factor affecting further changes in damage recovery for Dd’s ranging from 2.3 × 1011 to 3.8 × 1011 MeV/g when the annealing temperature varies between 175 and 300°C. For high Dd (greater than 2.3 × 1011 MeV/g) neutron irradiations, the annealing temperature significantly affects the damage recovery.