4H-SiC Pn Diode Research Articles

Comparison of Impact Ionization Models for 4H-SiC Along the <0001> Direction, Through Breakdown Voltage Simulations at Room Temperature

A comparative study of the simulated breakdown voltage of 4H-SiC devices has been conducted for the most widely used impact ionization models (Selberherr, Hatakeyama), based on the experimental data of 4H-SiC pn diodes. The effect of mesh density on the simulated breakdown voltage has been examined. The TCAD simulations employing default commercial simulators parameters did not converge to a value close to the experimentally observed as the mesh density is increased. Various experimental ionization parameters, as reported in the bibliography, have been examined instead of the commercial-TCAD-simulators default ones. Simulations with optimal parameters result in convergence to breakdown voltage values close to the experimentally measured ones when the mesh density is increased.

Magnetic Field Sensing with 4H SiC Diodes: N vs P Implantation

We explore the magnetic sensing capabilities of two 4H-SiC n+p diodes fabricated by NASA Glenn which only differ in the implanted ion species, nitrogen and phosphorus, and the implant activation annealing time. We use low-and high-field electrically detected magnetic resonance (EDMR) to investigate the defect structure used to sense magnetic fields as well as to evaluate the sensitivity. In addition, we expose these devices to high energy electron radiation to evaluate the defect sensing capability in a harsh radiation environment. The results from this work will allow us to tailor our processing methods to design a more optimal 4H-SiC pn diode for magnetic field sensing in harsh environments.

Extension of Stacking Faults in 4H-SiC pn Diodes under a High Current Pulse Stress

We investigated the expansion of stacking faults (SFs) under a high current pulse stress in detail. In situ observations showed bar-shaped SFs and two types of triangle SFs with different nucleation sites. The calculated partial dislocation velocity of the bar-shaped SFs was four times faster than that of the triangle SFs. The temperature dependence of the partial dislocation velocity was used to estimate activation energies of 0.23±0.02 eV for bar-shaped SFs and 0.27±0.05 eV for triangle SFs. We also compared the electrical characteristics before and after the stress. The forward voltage drop slightly increased by 0.05 V, and the leakage current did not increase.

Measuring depletion-layer capacitance to analyze a decrease in breakdown voltage of 4H-SiC diodes

A decrease in breakdown voltage (VBD) in the termination area of 4H-SiC PN diodes after 64 h reverse-bias stressing was analyzed. To analyze the VBD decrease, a novel analysis method based on the results of measuring depletion-layer capacitance of the PN diodes was proposed. The measurement results indicate that the positive-charge density (QTM) at the SiO2/SiC interface of the termination area increased after the reverse-bias stressing. Besides, in the case of QTM of 1012 cm−2 at the SiO2/SiC interface, the decrease in the measured capacitance showed the same tendency as the decrease in the simulated capacitance. By comparing the measured full depletion voltage and simulated full depletion voltage, the amount of QTM was estimated. It is thus concluded that the proposed method for measuring the depletion-layer capacitance is effective for analyzing the QTM change in the termination area.

Analyzing charge distribution in the termination area of 4H-SiC diodes by measuring depletion-layer capacitance

The distribution of positive-charge density at the SiO2/SiC interface of the termination area (QTM) was analyzed by measuring the depletion-layer capacitance of 4H-SiC PN diodes with different termination structures. A change in QTM induced by reverse-bias stressing (ΔQTM) caused a change in the breakdown voltage of the diodes. By comparing the measured depletion-layer capacitance to the simulated value, the initial QTM () and the distribution of ΔQTM were clarified. It is concluded from these results that the distribution of ΔQTM was not uniform but that positive charges mostly accumulated in the termination area under a high applied electric field.

Temperature sensor based on 4H-silicon carbide pn diode operational from 20 °C to 600 °C

A high-performance temperature sensor based on 4H-SiC pn diode is demonstrated. The sensor is capable of stable operation in a temperature range from 20 °C to 600 °C. The forward voltage of the pn diode has a linear dependence on temperature variation at a constant current, and recombination current dominates the current flowing in the 4H-SiC pn diode in the measured current range. At a forward current density of 0.44 mA/cm2, the device achieves a sensitivity of 3.5 mV/ °C. This type of temperature sensor can be integrated with SiC power management and control circuitry to create a sensing module that is capable of working at extremely high temperatures.

Current Transport Mechanisms in 4H-SiC PiN Diodes

Current transport mechanisms in 4H-SiC pn diodes have been investigated by current-voltage and under-bias-photoemission experiments. In low voltages (1.9 to 2.6 Volts) current recombination dominates forward current. Moreover, carrier recombination takes place on the perimeter of the diodes. From 2.6 to 2.8 Volts a mixed conduction with recombination and diffusion components or recombination through multielectron centers in the space charge region is observed.

Fabrication and Characterization of 4H-SiC pn Diode with Field Limiting Ring

Fabrication and Characterization of 4H-SiC pn Diode with Field Limiting Ring

4H-SiC pn Diode Grown by LPE Method for High-Power Applications

4H-SiC pn Diode Grown by LPE Method for High-Power Applications

Dynamic Characteristics of 6.2 kV High Voltage 4H-SiC pn Diode with Low Loss

A 4H-SiC pin diode with improved termination named mesa JTE has been developed and a high blocking voltage of 6.2kV and a low VF of 4.7V at 100A/cm2 have been achieved. A developed diode has a short reverse recovery time of 28.5ns at room temperature. By evaluation of reverse recovery characteristics, a developed diode has a minority carrier lifetime of longer than 1μs at 350°C in spite of a minority carrier lifetime of 64ns at room temperature. Furthermore, a developed diode has 1/29th lower recovery loss than those of a commercialized 4.5kV Si diode.

Comparison of 4H-SiC pn, Pinch and Schottky Diodes for the 3 kV Range

Comparison of 4H-SiC pn, Pinch and Schottky Diodes for the 3 kV Range

Electrical Characteristics of 4H-SiC pn Diode Grown by LPE Method

Electrical Characteristics of 4H-SiC pn Diode Grown by LPE Method

Design and fabrication of planar guard ring termination for high-voltage SiC diodes

An optimized multiple floating guard ring structure is investigated for the first time as an edge termination method for high voltage 4H-SiC planar devices. Simulations were performed to investigate SiC guard ring termination, and determine the optimum guard ring spacing for planar diodes with up to four floating rings. Simulated optimized designs predicted breakdown values from 40% of the ideal breakdown with a single ring, to 84% of the ideal value for diodes with four rings. Implanted 4H-SiC pn diodes with optimized guard ring designs were fabricated and results correlated to simulation. Experimental breakdown values of 1.2–1.3 kV for guard ring structure with four rings were in good agreement with simulated results.