Papers by Keyword: Schottky Diode

Abstract: Radiation-hardened SiC power devices are essential to prevent leakage degradation and catastrophic failures such as SEE and SEB. Lateral device structures lower the risk of contact shorting by providing greater physical separation between conductive regions. Wider device geometries also improve radiation tolerance, as larger dimensions can accommodate charge buildup with less effect on device performance. In addition, RESURF structures enhance robustness by shifting the high electric field into the bulk, which reduces the impact of radiation-sensitive interface states on breakdown.

Abstract: This study focuses on the trench etching process for the fabrication of SiC Superjunction Schottky diodes, utilizing an ICP-RIE technique. Through a series of experiments, we optimized the etching parameters, including ICP power, RF power, and SF₆ gas flow rates, to achieve etching rates ranging from 157 nm/min to 372.1 nm/min. Additionally, the study identified the performance of the hard mask as a critical issue during the etching process, which was improved by reducing the RF power below 80 w. The deepest trench achieved reached a depth of 21 μm at 75 w RF power, 1000 w ICP power and 40 sccm SF₆, confirming the feasibility of this approach for fabricating high-performance SiC superjunction devices.

Abstract: This paper shows results of SiC Schottky diodes fabricated without ion-implanted P-type regions. Diodes with blocking voltages up to 4,500 V are demonstrated utilizing an epitaxial P-type ring with sloped edges for the edge termination. Reverse-bias currents at temperatures higher than 60°C, and at nominal blocking voltages of 650 V, 1200 V, and 1700 V, are shown to match the theoretical values based on the two fundamental current mechanisms: tunneling and thermionic emission. In comparison to JBS and MPS diodes, the whole anode area is active, which enables homogeneous current flow and comparable isothermal characteristics without the usual wafer thinning. In addition, the non-thinned wafer results in larger thermal capacitance, allowing for higher repetitive peak surge currents for the same junction temperature within the maximum operating temperature of 175°C.

Abstract: In this work, we focus on the electrical characterization of Ni Schottky contact on n-type heavily doped (N_D>10¹⁹ cm⁻³) 4H-SiC layer, achieved by P-ion implantation. In particular, the forward current–voltage characterization of Schottky diodes showed a reduced turn-on voltage for the Ni/heavily-doped 4H-SiC if compared to a reference Ni/4H-SiC Schottky contact fabricated under similar conditions but without implant. Moreover, it was observed the predominance of a thermionic-field-emission (TFE) mechanism for the current transport through the interface. From a current-voltage-temperature (I-V-T) study, the temperature-dependence of the Schottky barrier and doping concentration were evaluated, obtaining a reduction of the barrier (from 1.77 to 1.66 eV), while the doping concentration maintains constant around 1.96×10¹⁹ cm^-3. This study provides useful insights for a deeper comprehension of the electrical behavior of Ni contacts and can have possible applications in 4H-SiC Schottky diode technology.

Abstract: A novel silicon carbide (SiC) trenched schottky diode with step-shaped junction barrier is proposed for superior static performance and large design window. In the proposed diode, to improve tradeoff between specific on-resistance and surface peak electric field, the shape of the trenched-junction is modified to stair-step, without extra fabrication process. To investigate the performances of the SiC step-shaped trenched junction barrier schottky (SSTJBS) diode, numerical simulations are carried out through Silvaco TCAD. The results indicate that the proposed diode can accommodate highly doped drift region with no degradation of its reverse blocking characteristic. In comparison with the conventional SiC trenched junction barrier schottky (TJBS) diode, the proposed SiC SSTJBS diode shows a larger design window of drift region doping concentration from 7.9×10¹⁵cm^-3 to 9.5×10¹⁵cm^-3. In the design window, the specific on-resistance and surface peak electric field can be reduced by 12.9% and 11%, respectively.

Abstract: The electrical behavior of silicon carbide charge-balance (CB) Schottky/JBS diodes is examined. Based on the observed electrical characteristics, a subcircuit SPICE model for the experimental devices is proposed and validated against the data. The proposed model consists of a standard SPICE diode with custom parameters along with a network of discrete resistive and reactive subcircuit elements required to replicate the complex static and dynamic behavior of the experimental devices. With proper selection of component values, static, dynamic, and temperature-dependent device behavior are well modelled from room temperature to 150°C.

Abstract: Tilt angles of threading dislocations (TDs) which induce leakage of current on SiC junction barrier schottky diodes (SiC-JBSs) were investigated by two-photon-excited photoluminescence (2PPL) and transmission electron microscopy (TEM). Observation of leakage spots measured by atomic force microscopy (AFM) revealed that pit-like structures were certainly formed but the depths were considerably shallow, indicating that influence of local electric field due to the structures was negligible on our SiC-JBSs. It became clear that tilt angles of the TDs inducing leakage were relatively larger than about 11° by 2PPL and that the TD was the threading mixed dislocation by TEM.

Abstract: In this paper, the impact of substrate preconditioning by ion bombardment in-situ in a conventional sputter equipment on n-doped 4H-silicon carbide (SiC) Schottky diodes with molybdenum nitride metallization is studied. By variation of the plasma power during argon ion bombardment, the effective barrier height is adjustable in the range from 0.66 to 0.96 eV, as deduced by current / voltage measurements over a wide temperature range. Therefore, this approach offers a straightforward method to tailor the Schottky barrier height over a significant range by introducing an insitu substrate pretreatment step available in most sputter equipment.

Abstract: This paper investigates the 10 ms surge current (I_FSM) and single-pulse avalanche energy (E_AS) limits of 1200 V/10 A SiC Schottky rectifiers from several commercial vendors. GeneSiC’s 1200 V/10 A diode recorded maximum I_FSM values of 162 A at T_C=25°C and 135 A at T_C=150°C, which were the highest amongst investigated devices. The diode sustains junction temperatures as high as 910°C during surge current operation, which results in eventual failure of the Aluminum based metallization.

Abstract: Modeling and simulation of 3C-SiC power devices such as MOSFETs and diodes requires a model for the breakdown field that is consistent with the Monte-Carlo-simulated ionization rates of electron and holes and supported by experimental results. The challenge one faces is the limited number of publications reporting such calculations and the limited availability of high-quality ionization breakdown data for 3C-SiC diodes. We therefore performed a series of 2D simulations of both n-type and p-type Schottky diodes and p⁺-n diodes that confirms the general breakdown field trend with doping density obtained from experiments. We uncovered a difference between n-type and p-type diode breakdown behavior, identified the discrepancy between the calculations and the experimental data, and extracted a simple breakdown field model, useful for further 3C-SiC device design and simulation.