Attempts to model the current through Schottky barrier diodes using the two fundamental mechanisms of thermionic emission and tunnelling are adversely impacted by defects and second order effects. ...This has led to the publication of countless different models to account for these effects, including some with non-physical parameters. Recently, we have developed silicon carbide Schottky barrier diodes that do not suffer from second order effects, such as excessive leakage, carrier generation and recombination, and non-uniform barrier height. In this paper, we derive the foundational current equations to establish clear links between the fundamental current mechanisms and the governing parameters. Comparing these equations with measured current-voltage characteristics, we show that the fundamental equations for tunnelling and thermionic emission can accurately model 4H silicon carbide Schottky barrier diodes over a large temperature and voltage range. Based on the obtained results, we discuss implications and misconceptions regarding barrier inhomogeneity, barrier height measurement, and reverse-bias temperature dependencies.
Characterization of near-interface traps (NITs) in commercial SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) is essential because they adversely impact both performance and ...reliability by reducing the channel carrier mobility and causing threshold-voltage drift. In this work, we have applied a newly developed integrated-charge technique to measure the density of NITs that are active in the above-threshold region of commercial SiC MOSFETs. The results demonstrate that NITs trap about 10% of the channel electrons for longer than 500 ns.
Silicon carbide (SiC) is one of the most promising materials for applications in harsh environments thanks to its excellent electrical, mechanical, and chemical properties. The piezoresistive effect ...of SiC has recently attracted a great deal of interest for sensing devices in hostile conditions. This paper reviews the piezoresistive effect of SiC for mechanical sensors used at elevated temperatures. We present experimental results of the gauge factors obtained for various poly-types of SiC films and SiC nanowires, the related theoretical analysis, and an overview on the development of SiC piezoresistive transducers. The review also discusses the current issues and the potential applications of the piezoresistive effect in SiC.
Due to superior material properties of SiC for high-voltage devices, SiC Schottky diodes are used in energy-conversion systems such as solar-cell inverters, battery chargers, and power modules for ...electric cars and unmanned aerial vehicles. The reliable operation of these systems requires the chip temperature of SiC Schottky diodes to be maintained within the limit set by the device package. This is especially crucial during surge-current events that dissipate heat within the device. As a thermal-management method, manufactures of commercial SiC Schottky diodes have introduced wafer thinning practices to reduce the thickness of the SiC chip and, consequently, to reduce its thermal resistance. However, this also leads to a reduction in the thermal capacitance. In this paper, we present experimental data and theoretical analysis to demonstrate that the reduced thermal capacitance has a much larger adverse effect in comparison to the beneficial reduction of the thermal resistance. An implication of the presented results is that, contrary to the adopted wafer thinning practices, SiC Schottky diodes fabricated without wafer thinning have superior surge-current capability.
This article reviews the development of SiC and GaN devices for power-switching applications in the context of four specifically identified application requirements: (1) high-blocking voltage, (2) ...high-power efficiency, (3) high-switching speed, and (4) normally OFF operation. Specific device and material characteristics, such as ON resistance, parasitic capacitances, and energy-gap values, are compared and discussed in relation to the identified application requirements. Following a review of the fundamental limitations of silicon as a material, this article describes the material advantages that motivated the development of commercially available Schottky diodes and transistors using SiC. The last section analyzes the potential of GaN to enable further technical progress beyond the theoretical limit of Si and to significantly reduce the cost of power-electronic switches.
The performance and reliability of the state-of-the-art power 4H-SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) are affected by electrically active defects at and near the interface ...between SiC and the gate dielectric. Specifically, these defects impact the channel-carrier mobility and threshold voltage of SiC MOSFETs, depending on their physical location and energy levels. To characterize these defects, techniques have evolved from those used for Si devices to techniques exclusively designed for the SiC MOS structure and SiC MOSFETs. This paper reviews the electrically active defects at and near the interface between SiC and the gate dielectric in SiC power MOSFETs and MOS capacitors. First, the defects are classified according to their physical locations and energy positions into (1) interface traps, (2) near interface traps with energy levels aligned to the energy gap, and (3) near-interface traps with energy levels aligned to the conduction band of SiC. Then, representative published results are shown and discussed for each class of defect.
Measurements of the near-interface oxide traps (NIOTs) aligned to the conduction band of silicon-carbide (SiC) are of particular importance as these active defects are responsible for degradation of ...the channel-carrier mobility in 4H-SiC MOSFETs. In this brief, a new method for measurement of the active NIOTs with energy levels aligned to the conduction band is proposed. The method utilizes transient-current measurements on 4H-SiC MOS capacitors biased in accumulation. Nitrided oxide and dry oxide are used to illustrate the applicability of the proposed measurement method.
The state-of-the-art 4H-SiC MOSFETs still suffer from performance (low channel-carrier mobility and high threshold voltage) and reliability (threshold voltage instability) issues. These issues have ...been attributed to a large density of electrically active defects that exist in the SiO2–SiC interfacial region. This paper reviews the earlier and the latest results about the responsible defects for the performance and reliability issues of SiC MOS devices, in the context of the evolution of physical understanding of these defects. The aim of this critical review is to clarify possible confusions due to inconsistencies between the earlier and the latest results. Specific clarifications relate to the physical position of the active defects (whether they are located at or near the SiO2–SiC interface) and the energy position of their energy levels (above or below the bottom of conduction band).
Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, ...excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors.
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