Gamma irradiation effects have been investigatedon 4H-silicon carbide (SiC) bipolar junction transistors (BJTs),where the devices were exposed under different biasing regimessuch as saturation, cut-off, active, reverse, and zero bias. Sincebipolar transistors can be affected by dose rate, three differentdose rates were used during irradiation tests. Characterizationwas performed on the transistors, without irradiation but in situto avoid delays between irradiation and characterization. Thestudy explores the relationship between biasing conditions andtheir impact on radiation-induced degradation of SiC BJTtransistors. From these experiments, it is clear that 4H-SiCbipolar transistors can withstand high gamma doses, in the worstcase less than 22% degradation of the current gain was seen fordoses of up to 2 Mrad(Si).

In this study, we introduce the impact of gamma irradiation on 4H-SiC based transistor-transistor logic (TTL) inverters. These monolithic bipolar inverters have been successfully demonstrated in a broad spectrum of temperature and supply voltage conditions. In this iteration of experiments, attempts made to the processing to increase beta values. The gamma radiation tests from a60 Co source were conducted under various operation conditions and measured in-situ under different biasing conditions. The Silicon Carbide Integrated circuits ( SiC ICs) show excellent tolerance properties to gamma radiation up to doses of nearly 1 MRad. Comparable Si BJT-based TTL inverters show considerable degradation already at one order of magnitude lower doses, clearly demonstrating the superior radiation hardness of 4H-SiC ICs.

In this study, we investigate the impact of Gamma Radiation on 4H Silicon Carbide (SiC) Transistor-Transistor Logic (TTL) integrated circuits (ICs), particularly focusing on inverters processed with distinct types of interface oxides: Thermally Grown, Chemical Vapor Deposition, and Atomic Layer Deposition. This research was conducted using a60Co source at Hiroshima University, applying varied radiation doses (17.9 rad(Si)/s, 7.3 rad(Si)/s, and 2.47 rad(Si)/s) to assess the resilience of the SiC inverters under these conditions. Our findings reveal that thermal oxides (Batch 1: W1 and W2) demonstrate higher radiation resilience compared to ALD and CVD interface oxides (Batch 2: W3 and W4), attributable to their denser structure and fewer defects. The study also identifies that while the inverters exhibit marginal degradation at gamma doses nearing 700 krad (under 6%), the most critical operational state is the passive mode (VCC = VIN = 0 V), where the build-up of induced charge in the oxide and interface may lead to early IC degradation of the noise margins. The outcomes from this research provide insights into the processing flow and enhancement of SiC electronics. Our results underscore the potential of SiC-based ICs in environments with high radiation levels, such as space missions, nuclear reactors, and medical applications, due to their enhanced radiation tolerance.

Silicon carbide (SiC) is a key material for electronics operating in harsh environments due to its wide bandgap, high thermal conductivity, and radiation hardness. In this work, we present a SPICE model for a 4H-SiC BJT and TTL inverter exposed to gamma radiation. The devices were fabricated using a dedicated SiC bipolar process at KTH (Sweden) and tested at the 60Co Calliope (Italy) facility up to 800 krad (Si). Experimental data, including Gummel plots and inverter transfer characteristics, were used to calibrate and refine a VBIC-based SPICE model. The adjusted model accounts for both bulk and surface degradation mechanisms by extracting parameters of forward current gain (beta F), saturation current (IS), base resistance (RB), and forward transit time (TF). Results show a uniform degradation of BJTs, primarily manifested as reduced current gain and increased base resistance, while the inverter maintained functional operation up to 600 krad(Si). Extrapolation of the SPICE model predicts a failure threshold near 16 Mrad(Si), far exceeding the tolerance of conventional silicon circuits. By linking radiation-induced defects at the material and interface levels to circuit-level behavior, the proposed model enables realistic design and lifetime prediction of SiC integrated circuits for satellites, planetary missions, and other radiation-intensive applications.

This paper investigates the effects of 60Co gamma irradiation on the performance of 4H-SiC Bipolar Junction Transistors (BJTs) at a temperature of -70°C. Building upon previous research that identified the zero-bias condition as the most critical biasing regime for these devices at room temperature, this study extends the investigation to low-temperature environments pertinent to various extreme applications, such as space missions. In-situ electrical measurements, specifically monitoring the common-emitter current gain β, were performed during irradiation at two different dose rates: 50 rad (Si)s and 200 radSi)s. The results demonstrate a significantly increased radiation-induced degradation of the current gain at -70°C compared to room temperature. Furthermore, a pronounced Enhanced Dose Rate Sensitivity (EDRS) was observed at this low temperature, with higher degradation occurring at the lower dose rate of 50 rad(Si)s. These findings underscore the critical importance of considering temperature effects in the qualification of SiC devices for radiation-hardened applications, particularly in scenarios where devices operate in a zero-bias state at low temperatures.