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The study focuses on analysing the high-level carrier lifetime (tau(HL)) in 4H silicon carbide (4H-SiC) PiN diodes under varying temperatures and proton implantation doses. The objective is to identify an empirical law applicable in technology computer-aided design (TCAD) modelling for SiC devices, describing the dependence of carrier lifetime on temperature to gain insights into how irradiation dose may influence the tau(HL). We electrically characterize diodes of different diameters subjected to different proton irradiation doses and examine the variations in current-voltage (I-V) and ideality factor (n) curves under various irradiation conditions. The effects of proton irradiation on the epitaxial layer are analysed through capacitance-voltage (C-V) measurements. We correlate the observed effects on I-V, n, and C-V curves to the hypothesis of formation of acceptor-type defects related to carbon vacancies, specifically the Z(1/2) defects generated during the irradiation process. The impact of irradiation on carrier lifetime is investigated by measuring tau(HL) using the open circuit voltage decay (OCVD) technique at different temperatures on diodes exposed to various H+ irradiation doses with constant ion energy. This investigation reveals the presence of a proportional relationship between 1/ tau(HL) and the dose of irradiated protons: the proportionality coefficient, referred to as the damage coefficient (K-T), exhibits an Arrhenius-type dependence on temperature. OCVD-measured lifetime on the various diodes demonstrates a power-law dependence of lifetime on temperature. The exponent of this dependence varies with the irradiation dose, notably showing an increase in temperature dependence at the highest H+ ion dose. This suggests a threshold-like dependence on H+ irradiation dose in the tau(HL) -temperature relationship., QC 20240620

In this work, MeV alpha particles generated from an accelerator are used to study single event breakdown (SEB) in 4H-SiC MOSFET samples, rated at 3.3 kV. The samples are exposed to bursts of alpha particles under reverse bias conditions to investigate the SEB sensitivity to ion energy and reverse bias. The energies of alpha particles are chosen to reach different depths in the drift region of the MOSFET devices, and also to penetrate the whole drift region. Forward and reverse characteristics are measured after each exposure, as long as no failures occur, to ensure that the device performance is maintained. The measurements show that no significant effects are observed on the drain-source leakage current, while minor effects on gate behavior can be seen as a function of accumulated fluence. Furthermore, SEB can only be triggered with a reverse bias larger than, or equal to 3 kV. A standard MOSFET cell with a similar rated voltage is also simulated in Sentaurus TCAD to study these effects, using two different models for the incident ion-induced ionization: the Alpha Particle and the Heavy Ion model. Simulations show that the Alpha Particle model cannot induce any device failures even with a 3.5 kV reverse bias, while it is possible to trigger a failure by the Heavy Ion model, where the ionization can be selected. Carrier plasma and internal electric field distributions of the two models are plotted and compared, showing that device failures triggered by a heavy ion are related to the hole injection at epi-substrate interface, in which linear energy transfer (LET) of the particle plays an important role., QC 20240522

QC 20240522

Self-charging power systems (SCPSs) are envisioned as promising solutions for emerging electronics to mitigate the increasing global concern about battery waste. However, present SCPSs suffer from large form factors, unscalable fabrication, and material complexity. Herein, a type of highly stable, eco-friendly conductive inks based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are developed for direct ink writing of multiple components in the SCPSs, including electrodes for miniaturized spacer-free triboelectric nanogenerators (TENGs) and microsupercapacitors (MSCs), and interconnects. The principle of “one ink, multiple functions” enables to almost fully print the entire SCPSs on the same paper substrate in a monolithic manner without post-integration. The monolithic fabrication significantly improves the upscaling capability for manufacturing and reduces the form factor of the entire SCPSs (a small footprint area of ≈2 cm × 3 cm and thickness of ≈1 mm). After pressing/releasing the TENGs for ≈79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while the 6-cell array to 3.0 V. On-paper SCPSs are promising to serve as lightweight, thin, sustainable, and low-cost power supplies., QC 20240514

Gamma irradiation effects have been investigated on 4H-silicon carbide (SiC) bipolar junction transistors (BJTs), where the devices were exposed under different biasing regimes such as saturation, cut-off, active, reverse, and zero bias. Since bipolar transistors can be affected by dose rate, three different dose rates were used during irradiation tests. Characterization was performed on the transistors, without irradiation but in situ to avoid delays between irradiation and characterization. The study explores the relationship between biasing conditions and their impact on radiation-induced degradation of SiC BJT transistors. From these experiments, it is clear that 4H-SiC bipolar transistors can withstand high gamma doses, in the worst case less than 22% degradation of the current gain was seen for doses of up to 2 Mrad(Si)., QC 20240201

A comparison of the displacement damage effects in Si and silicon carbide (4H-SiC) commercial diodes due to 6 MeV proton irradiation is presented. The devices chosen for this study are rated at 650 V/8 A, making them technological alternatives of each other. It is found that Si diodes degrade ≈4.6 times faster than the SiC counterparts under forward biasing. In addition, the leakage current for the SiC diode in reverse mode decreases due to proton irradiation, whereas it increases for the Si diode under the same conditions. The difference in the behavior of both the diodes, as a result of the irradiation process, is discussed in terms of the induced deep-level defects. The results show that SiC diodes are more resistant to displacement damage caused by proton irradiation than Si devices, with the same specifications., QC 20240702

Proton Implantation, Shockley-Read-Hall (SRH) Lifetime, IV characteristics, reverse recovery. Abstract. In this paper, Shockley-Read-Hall (SRH) lifetime depth profiles in the drift layer of 10 kV SiC PiN diodes are calculated after MeV proton implantation. It is assumed that the carbon vacancy is the domination trap for charge carrier recombination and the SRH lifetime is calculated with defect parameters from the literature and proton-induced defect distributions deduced from SRIM calculations. The lifetime profiles are imported to Sentaurus TCAD and static and dynamic simulations using tailored lifetime profiles are carried out to study the electrical effect of proton implantation parameters. The results are compared to measurements, specializing on optimization of the trade off between on-state and turn-off losses, represented by the forward voltage drop, VT, and reverse recovery charge, Qrr, respectively. Both the simulated and measured IV characteristics show that increasing proton dose, or energy, has the effect on increasing forward voltage drop and on-state losses, while simultaneously, the localized SRH lifetime drop decreases the plasma level, increases the speed of recombination and decreases reverse recovery charge. Finally, TCAD simulations with different combinations of proton energies and fluences are used to optimize the trade-off between static and dynamic performances. Reverse recovery charge and forward voltage drops of these groups of diodes are plotted together, showing that a medium energy which induces the most defects in the depletion region relatively close to the anode gives the best dynamic performances, with a minimum degradation of static performance., QC 20230725

Covalent amorphous semiconductors, such as amorphous silicon (a-Si) and germanium (a-Ge), are commonly believed to have localized electronic states at the top of the valence band and the bottom of the conduction band. Electrical conductivity is thought to occur through the hopping mechanism via these localized states. The carrier mobility of these materials is usually very low, in the order of similar to 10(-3)-10(-2) cm(2)/Vs at room temperature. In this study, we show that pure high-density amorphous Ge has exceptionally high carrier mobility, in the order of similar to 100 cm(2)/Vs, and a high hole concentration of similar to 10(18) cm(-3). The temperature-dependent conductivity of the material is also very-well defined with two distinctive regions, extrinsic and intrinsic conductivity, as in crystalline Ge. These results provide direct evidence for a largely preserved band structure and non-localized states within the valence band in high-density amorphous Ge, as previously suggested by Tauc et al. from optical characterization alone., QC 20230508

QC 20230612

In this paper, proton implantation with different combinations of MeV energies and doses from 2x109 to 1x1011 cm-2 is used to create defects in the drift region of 10 kV 4H-SiC PiN diodes to obtain a localized drop in the SRH lifetime. On-state and reverse recovery behaviors are measured to observe how MeV proton implantation influences these devices and values of reverse recovery charge Qrr are extracted. These measurements are carried out under different temperatures, showing that the reverse recovery behavior is sensitive to temperature due to the activation of incompletely ionized p-type acceptors. The results also show that increasing proton implantation energies and fluencies can have a strong effect on diodes and cause lower Qrr and switching losses, but also higher on-state voltage drop and forward conduction losses. The trade-off between static and dynamic performance is evaluated using Qrr and forward voltage drop. Higher fluencies, or energies, help to improve the turn-off performance, but at a cost of the static performance.