http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

A marigold-like SiC@MoS2 nanoflower with a unique Z-scheme structure efficiently achieves the overall conversion of gas phase CO2 with H2O (CO2 (g) + 2H2O (g) = CH4 + 2O2) without any sacrificial reagents under visible light (λ ≥ 420 nm) irradiation. The CH4 and O2 evolution are 323 and 621 μL·g-1·h-1, and stable throughout 5 cycle reactions of total 40 h. This work demonstrates a breakthrough in artificial photosynthesis with the Z-scheme 1D heterojunction constructed by combining 2D semiconductor and 3D semiconductor based on the transfer balance of photogenerated electron and hole.

Visible-Light Driven Overall Conversion of CO2 and H2O to CH4 and O2 on 3D-SiC@2D-MoS2 Heterostructure.

The need for power semiconductor devices with high-voltage, high- frequency, and high-temperature operation capability is growing, especially for advanced power conversion and military applications, and hence the size and weight of the power electronic system are reduced. Development of 15-kV SiC IGBTs and their impact on utility applications is discussed.

Smart grid technologies

Simple analytical approximation has been obtained to describe the temperature and concentration dependencies of the low-field mobility in gallium nitride (GaN) in wide temperature (50⩽ T ⩽1000 K) and concentration (10 14 ⩽ N ⩽10 19 cm −3 ) ranges. The dependence of the temperature T m at which the mobility μ is at a maximum on the doping level is also obtained. Results obtained can be directly used for computer simulation of GaN-based devices.

Carrier mobility model for GaN

This paper presents a comprehensive short-circuit ruggedness evaluation and numerical investigation of up-to-date commercial silicon carbide (SiC) MOSFETs. The short-circuit capability of three types of commercial 1200-V SiC MOSFETs is tested under various conditions, with case temperatures from 25 to 200 °C and dc bus voltages from 400 to 750 V. It is found that the commercial SiC MOSFETs can withstand short-circuit current for only several microseconds with a dc bus voltage of 750 V and case temperature of 200 °C. The experimental short-circuit behaviors are compared, and analyzed through numerical thermal dynamic simulation. Specifically, an electrothermal model is built to estimate the device internal temperature distribution, considering the temperature-dependent thermal properties of SiC material. Based on the temperature information, a leakage current model is derived to calculate the main leakage current components (i.e., thermal, diffusion, and avalanche generation currents). Numerical results show that the short-circuit failure mechanisms of SiC MOSFETs can be thermal generation current induced thermal runaway or high-temperature-related gate oxide damage.

Temperature-Dependent Short-Circuit Capability of Silicon Carbide Power MOSFETs

The specific features of the temperature and bias dependences of the switch-on gate current in SiC thyristors are examined analytically for two possible switching mechanisms. The so-called ?-mechanism, which is highly typical of the conventional Si thyristors, is characterized by very weak temperature and bias dependences. By contrast, the so-called ?-mechanism, which is very characteristic of SiC thyristors, is highly sensitive to changes in temperature and bias. If the thyristor is switched on by the ?-mechanism, the switch-on gate current density decreases very steeply with increasing temperature. As a result, the thyristor can lose its working capacity at elevated temperatures due to the instability against even very weak impacts. With decreasing the bias voltage Ua, the gate switch-on current increases very steeply, which can make switching the thyristor on difficult. The unintentional shunting, which is apparently present in high-voltage SiC thyristors, causes the transition from the ?- to the ?-mechanism at elevated temperatures and high biases. It can be supposed that introduction of a controllable technological shunting of the emitter?thin base junction allows stabilization of the temperature and bias parameters of SiC thyristors. The analytical results are confirmed by computer simulations performed in wide temperature and bias ranges for a 4H-SiC thyristor of the 18 kV class.

Specific features of the switch-on gate current and different switch-on modes in silicon carbide thyristors

Transport phenomena in Schottky diodes are analyzed at high injection levels of minority carriers. It is shown that the correct description of these phenomena requires that the mode of diffusion stimulated by the quasi-neutral drift (DSQD) should be considered. An analytical expression for current–voltage characteristics of a Schottky diode at high injection levels is derived. The expression predicts a seemingly paradoxical result: the higher the base doping level, the higher the voltage drop across a diode at the same current density. The analytical results are confirmed by computer simulations. The results may be important for analyses of SiC Junction Barrier Schottky (JBS) diodes at very high current densities (surge current mode).

Minority carrier injection and current–voltage characteristics of Schottky diodes at high injection level

The influence of the combined effects of high injection level and heavy doping on the characteristics of silicon p + –n–n + solar cells is examined. The total amount of nonlinear physical phenomena (Auger recombination, electron-hole scattering, band-gap narrowing, charge carrier lifetime and transport coefficient reduction in the heavily doped layers of the structure) is taken into account. It has been established that a combined process which includes the generated charge carrier overflowing from n-base layer to highly doped n + -type and p + -type layers of the structure and their subsequent recombination in these highly doped layers, proves to be of great importance in silicon solar cells. The influence of electron-hole scattering on charge carrier transport in the highly doped n + -type and p + -type layers has been investigated for the first time. It has been found that minority carrier complete drag phenomenon results in a significant decrease of n + -type and p + -type layer saturation currents.

Effect of nonlinear physical phenomena on the photovoltaic effect in silicon p + -n-n + solar cells

Criteria for occurrence of the quasineutral diffusion mode have been investigated in terms of a generalized approach that takes into account the dependences of the electron and hole velocities on the electric field. These criteria should be used to describe the carrier transport in bases of forward biased bipolar semiconductor devices (diodes, thyristors, and power bipolar transistors in the saturation mode). The criteria appreciably differ from the previously obtained commonly accepted criteria. It is demonstrated that equations describing the carrier transport in the quasineutral approximation in n- and p-type semiconductors are different. These equations are used to obtain analytical conditions in which the diffusion mode is operative. The applicability limits of the diffusion approximation in simulation of semiconductor structures are found. The analytical results are confirmed by a numerical experiment.

Physical limitations of the diffusive approximation in semiconductor device modeling

A new mechanism for the formation of critical turn-on charge is shown to exist in thyristor structures. A new analytical model that makes it possible to derive the relations that define the critical charge in modern thyristor structures based on either Si or a new SiC material is suggested. The validity of the suggested analytical model of critical charge is verified using a numerical simulation.

Tigran T. Mnatsakanov

Papers

Specific features of the switch-on gate current and different switch-on modes in silicon carbide thyristors

Minority carrier injection and current–voltage characteristics of Schottky diodes at high injection level

Effect of nonlinear physical phenomena on the photovoltaic effect in silicon p + -n-n + solar cells

Physical limitations of the diffusive approximation in semiconductor device modeling

A new physical mechanism for the formation of critical turn-on charge in thyristor structures