The ON-state characteristics of a 1.7-kV 4H-SiC junction barrier Schottky diode were studied after 4.5-MeV electron irradiation. Irradiation doses were chosen to cause a light, strong, and full doping compensation of an epitaxial layer. The diodes were characterized using Deep Level Transient Spectroscopy, C-V (T), and I-V measurements without postirradiation annealing. The calibration of model parameters of a device simulator, which reflects the unique defect structure caused by the electron irradiation, was verified up to 2000 kGy. The quantitative agreement between simulation and measurement requires: 1) the Shockley-Read-Hall model with at least two deep levels on the contrary to ion irradiation and 2) a new model for enhanced mobility degradation due to radiation defects. The diode performance at high electron fluences is shown to be limited by the doping compensation at the epitaxial layer.

Radiation resistance of state‐of‐the‐art commercial wide‐bandgap power transistors, 1700 V 4H‐SiC power MOSFETs and 200 V GaN HEMTs, to the total ionization dose was investigated. Transistors were irradiated with 4.5 MeV electrons with doses up to 2000 kGy. Electrical characteristics and introduced defects were characterized by current–voltage (I–V), capacitance–voltage (C–V), and deep level transient spectroscopy (DLTS) measurements. Results show that already low doses of 4.5 MeV electrons (>1 kGy) cause a significant decrease in threshold voltage of SiC MOSFETs due to embedding of the positive charge into the gate oxide. On the other hand, other parameters like the ON‐state resistance are nearly unchanged up to the dose of 20 kGy. At 200 kGy, the threshold voltage returns back close to its original value, however, the ON‐state resistance increases and transconductance is lowered. This effect is caused by radiation defects introduced into the low‐doped drift region which decrease electron concentration and mobility. GaN HEMTs exhibit significantly higher radiation resistance. They keep within the datasheet specification up to doses of 2000 kGy. Absence of dielectric layer beneath the gate and high concentration of carriers in the two dimensional electron gas channel are the reasons of higher radiation resistance of GaN HEMTs. Their degradation then occurs at much higher doses due to electron mobility degradation.

A comprehensive study of displacement damage and total ionisation dose effects on 4H-silicon carbide power devices is presented. Power diodes and transistors produced by different manufacturers were irradiated by high-energy particles (protons, alphas, electrons and neutrons). The influence of radiation on device characteristics was determined, the introduced radiation defects were identified, and the main degradation mechanisms were established. Results show that radiation leads to the creation of acceptor traps in the lightly doped drift regions of irradiated devices. Devices then degrade due to the removal of the carriers and the decrease in carrier mobility and lifetime. For unipolar devices, the gradual increase of the forward voltage is typical while the blocking characteristics remain nearly unchanged. In bipolar devices, high introduction rates of defects cause a sharp reduction of carrier lifetime. This results in shorter carrier diffusion lengths and subsequent loss of conductivity modulation leading to a sharp increase of the forward voltage drop. The irradiation also shifts the threshold voltage of power switches. That is critical, namely for metal-oxide-semiconductor field-effect transistors. According to the authors' study, the junction barrier Schottky diode and junction field-effect transistor (JFET) can be considered the most radiation-resistant SiC power devices.

Application of radiation defects for lifetime control in contemporary SiC PiN diodes was investigated using the calibrated device simulator ATLAS from Silvaco, Inc. Recombination models accounting for the effect of deep levels introduced by the irradiation were set according to experimental results obtained by C-V and DLTS measurements performed on low-doped n-type SiC epilayers irradiated with 4.5 MeV electrons and 670 keV protons. Global (4.5 MeV electron irradiation) and local (700 keV proton irradiation) lifetime reduction was then applied on the 2A/10kV SiC PiN diode and the ON-state and reverse recovery characteristics were simulated and compared. Results show that the proton irradiation can substantially improve the trade‑off between the diode ON‑state and turn‑OFF losses. Compared to the electron irradiation, the local lifetime killing by protons allows achieving better trade-off and softer recovery curves.

The effect of neutron, electron and ion irradiation on electrical characteristics of unipolar 1700V SiC power devices (JBS diodes, JFETs and MESFETs) was investigated. DLTS investigation showed that above mentioned projectiles introduce similar deep acceptor levels (electron traps) in the SiC bandgap which compensate nitrogen shallow donors and cause majority carrier (electron) removal. The key degradation effect occurring in irradiated devices is the increase of the ON-state resistance which is caused by compensation of the low doped n-type epilayer and simultaneous lowering of electron mobility. In the case of SiC power switches (JFET, MOSFET), these effects are accompanied by the shift of the threshold voltage. Radiation defects introduced in SiC power devices is unstable and some defects anneal out already at operation temperatures (below 175°C). However, this does not have significant effect on device characteristics.

In this article, the effect of local radiation damage on the electrical characteristics of 1700 V 4H-SiC Merged-Pin Schottky (MPS) diode have been investigated. Radiation defects introduced by irradiation with 670 keV protons were placed into the low-doped n-type epi-layer and their influence on diode characteristics were characterized by capacitance DLTS, C-V profiling and I-V measurements. Simulation model accounting for the effect of proton irradiation was developed, calibrated and used for analysis of underlying effects and temperature dependencies. Results show that the forward voltage drop and breakdown voltage is insensitive to the position of the damage region when the defect peak is placed far away from the Schottky metal contact of the MPS diode. However, when the damage region approaches to the regions, forward voltage drop degrades significantly. For fluences higher than cm , the acceptor concentration in the peak region achieves donor doping level of the epi-layer and a sharp increase in the diode forward voltage drop is observed. Acceptor centers introduced by proton irradiation also slightly increase the breakdown voltage while decreasing the leakage current at voltages close to the MPS diode breakdown ( V).

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The effect of neutron irradiation on commercial vertical high voltage normally-OFF SiC power N-JFETs was investigated. JFETs were irradiated with 1 MeV neutron equivalent fluences up to cm . Measurement showed that fast neutrons introduce deep levels acting mostly as deep acceptor centers. These centers gradually compensate lightly doped channel and drift regions of JFETs. As a result, characteristics are deteriorated, the JFET threshold voltage gradually increases and transconductance is lowered. At fluences higher than cm , the low doped n-regions are fully compensated and transistor loses its functionality. The 2D physical model of JFET in ATLAS simulator was developed and calibrated including the neutron irradiation effects. Simulation showed a good agreement with experimental data. This confirmed that carrier removal in the channel and drift region by acceptors centers introduced by neutrons is a dominant reason of SiC JFET degradation. Index Terms-Junction field effect transistor (JFET), neutrons, radiation effects, silicon carbide (SiC).