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This article explores modeling the thermal process of a Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (mosfet) power module through a finite element analysis (FEA) based full-order thermal model (FOM) and then reducing the order of the FEA thermal model using a hybrid model order reduction (MOR) method. This hybrid MOR method takes advantage of Krylov subspace projection method's ability to be applied to higher order systems and the controllable error bound of the Hankel singular value based MOR method using a pure mathematical approximation process without any heuristic assumption. The resulting reduced-order thermal model has a significantly reduced computation cost compared to the FEA model while preserving the accuracy of the FEA model with controllable error bounds. The proposed method is applied to a SiC mosfet power module to generate reduced-order thermal models, which are validated by computer simulation with respect to the FEA thermal model and are compared with a state-of-the-art three-dimensional thermal equivalent circuit model and the reduced-order thermal models generated by using a Krylov subspace projection method. Experimental validation of the thermal models with respect to the measured SiC mosfet junction temperature is provided. The results demonstrate higher accuracy and controllable error bound of the proposed method.

To improve the efficiency of a solar cell application, two areas of focus are necessary. The first is to improve the quality of the solar panels; and the second is to increase the inverter efficiency, which can be accomplished by using high frequency switches with low on-state and switching losses. GaN has a significantly bigger bandgap compared to Si material, resulting in higher breakdown voltage. Also, the channel lengths of GaN MOSFETs are smaller and, therefore, have smaller gate-to-source and drain-to-source capacitance. In this work, different GaN switches are characterized through their steady state and switching characteristics. Also, the use of GaN switches in some Solantro Semiconductor Corp. applications and a comparison of the total power losses of Si and SiC switches are also presented.

Obtaining a high coefficient of efficiency for a power converter requires that the components used to build it are well chosen. Power semiconductor switches are responsible for significant power loss. For the same breakdown voltage, a silicon carbide (SiC) bipolar device has a significantly thinner, lightly doped drift region (n- base) compared to silicon (Si) devices and, therefore, low switching losses and low voltage drops in the drift region. The forward voltage drop of a bipolar device is the sum of the drift region voltage drop and the junction voltages. The junction voltages of a Si device are significantly smaller as compared to a SiC device since its band gap is smaller. Therefore, for lower voltage devices (< 6.5 kV), the forward voltage drop will be smaller for Si as compared to SiC devices. For high voltage devices, the opposite is true. In this work, physics-based models of Si and SiC diodes were used to calculate the forward voltage drop for different breakdown voltages; and the simulation results are compared to determine the difference between Si and SiC devices.

This paper discusses extrapolations of current silicon power device technology into the future, followed by discussions of wide band gap (WBG) power devices with a focus on silicon carbide and gallium nitride. Other WBG materials are included from carbon, such as diamond and nanotubes, to various nitrides. Far future material development, that may impact power electronic devices decades out, is also discussed.

As femtosecond (fs) laser machining advances from micro/nanoscale to macroscale, approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand. In this research, an fs laser sharp shaping approach was developed to address two key challenges in macroscale machining (i.e. defects on edges and tapered sidewalls). The evolution of edge sharpness (edge transition width) and sidewall tapers were systematically investigated through which the dilemma of simultaneously achieving sharp edges and vertical sidewalls were addressed. Through decreasing the angle of incidence (AOI) from 0° to −5°, the edge transition width could be reduced to below 10 µm but at the cost of increased sidewall tapers. Furthermore, by analyzing lateral and vertical ablation behaviors, a parameter-compensation strategy was developed by gradually decreasing the scanning diameters along depth and using optimal laser powers to produce non-tapered sidewalls. The fs laser ablation behaviors were precisely controlled and coordinated to optimize the parameter compensations in general manufacturing applications. The AOI control together with the parameter compensation provides a versatile solution to simultaneously achieve vertical sidewalls as well as sharp edges of entrances and exits for geometries of different shapes and dimensions. Both mm-scale diameters and depths were realized with dimensional precisions below 10 µm and surface roughness below 1 µm. This research establishes a novel strategy to finely control the fs laser machining process, enabling the fs laser applications in macroscale machining with micro/nanoscale precisions.

To improve the efficiency of a solar cell application, two areas of focus are necessary. The first is to improve the quality of the solar panels; and the second is to increase the inverter efficiency, which can be accomplished by using high frequency switches with low on-state and switching losses. GaN has a significantly bigger bandgap compared to Si material, resulting in higher breakdown voltage. Also, the channel lengths of GaN MOSFETs are smaller and, therefore, have smaller gate-to-source and drain-to-source capacitance. In this work, different GaN switches are characterized through their steady state and switching characteristics. Also, the use of GaN switches in some Solantro Semiconductor Corp. applications and a comparison of the total power losses of Si and SiC switches are also presented.

Obtaining a high coefficient of efficiency for a power converter requires that the components used to build it are well chosen. Power semiconductor switches are responsible for significant power loss. For the same breakdown voltage, a silicon carbide (SiC) bipolar device has a significantly thinner, lightly doped drift region (n- base) compared to silicon (Si) devices and, therefore, low switching losses and low voltage drops in the drift region. The forward voltage drop of a bipolar device is the sum of the drift region voltage drop and the junction voltages. The junction voltages of a Si device are significantly smaller as compared to a SiC device since its band gap is smaller. Therefore, for lower voltage devices (< 6.5 kV), the forward voltage drop will be smaller for Si as compared to SiC devices. For high voltage devices, the opposite is true. In this work, physics-based models of Si and SiC diodes were used to calculate the forward voltage drop for different breakdown voltages; and the simulation results are compared to determine the difference between Si and SiC devices.