P. A. Ivanov

Collector conductivity modulation in 1200-V 4H-SiC BJTs (Modeling)

The resistance of the BJT collector layer can be sharply reduced by the effective injection of minority carriers (holes) from base to collector. As a result, the voltage drop across the BJT becomes substantially lower. The conditions under which this process can occur are the short rise time and the high amplitude of the base pulse.

Surge current capabilities and isothermal current–voltage characteristics of high-voltage 4H-SiC junction barrier Schottky rectifiers

Isothermal forward current?voltage characteristics of high-voltage 4H-SiC junction barrier Schottky rectifiers (JBS) have been studied for the first time. Isothermal characteristics were measured with JBS having a blocking voltage of 1700?V up to a current density j?????4200?A?cm?2 in the temperature range 297?460?K. Quasi-isothermal current?voltage characteristics of these devices were studied with injection of minority carriers (holes) up to j?????7200?A?cm?2 and ambient temperatures of 297 and 460?K. The isothermal forward current?voltage characteristics make it possible to numerically calculate (for example, by an iteration procedure) the overheating in an arbitrary operation mode.

Transient switch-off of a 4H-SiC bipolar transistor from the deep-saturation mode

The transient switch-off of a bipolar 4H-SiC transistor from the deep-saturation mode is studied by performing 1D numerical simulation. Switch-off in the zero base current mode and in the mode of switching-off with a negative base current is examined. It is shown that at quite real values of the switching-off base current, the switch-off time can be made ~40 times shorter than the switch-off time at zero base current. The delay time can also be made substantially (several times) shorter. It is noted that, in the deep saturation mode in which the conductivity of the collector layer is highly modulated by minority carriers, the bipolar transistor can operate in the continuous mode at a rather high current density.

On the Spatial Localization of Free Electrons in 4 H -SiC MOSFETS with an n Channel

The problem of the spatial localization of free electrons in 4H-SiC metal—oxide—semiconductor field effect transistors (MOSFETS) with an accumulation- and inversion-type n channel is theoretically analyzed. The analysis demonstrates that, in optimally designed accumulation transistors (ACCUFETs), the average distance from the surface, at which free electrons are localized, may be an order of magnitude larger than that in inversion MOSFETs. This can make 4H-SiC ACCUFETs advantageous as regards the effective carrier mobility in a conducting channel.

Current–voltage characteristics of high-voltage 4 H -SiC p + – n 0 – n + diodes in the avalanche breakdown mode

Abstractp+–n0–n+ 4H-SiC diodes with homogeneous avalanche breakdown at 1860 V are fabricated. The pulse current–voltage characteristics are measured in the avalanche-breakdown mode up to a current density of 4000 A/cm2. It is shown that the avalanche-breakdown voltage increases with increasing temperature. The following diode parameters are determined: the avalanche resistance (8.6 × 10–2 Ω cm2), the electron drift velocity in the n0 base at electric fields higher than 106 V/cm (7.8 × 106 cm/s), and the relative temperature coefficient of the breakdown voltage (2.1 × 10–4 K–1).

Electrical Performance of 4H-SiC Based Drift Step Recovery Diodes

Mesa-epitaxial 4H-SiC p+-p-no-n+-diodes were fabricated from commercial epitaxial wafers. Reverse recovery characteristics of the diodes were measured in pulse regimes to be relevant to operation of drift step recovery diodes (DSRDs) [1]. When injecting the minority carriers by forward current pulse followed by applying a reverse voltage pulse, the diodes are able to break the reverse current in a subnanosecond time (DSRD-mode). Different regimes of diode operation in DSRD-mode are investigated such as variable reverse voltage amplitude, forward current amplitude and duration, time delay between forward and reverse pulses.

Low Frequency Noise in 4H-SiC Schottky Diodes Under Forward Bias

The 1/f noise has been investigated for the first time at 300 and 77 K in high-quality 4H-SiC Schottky diodes. It is shown that, that at 77 K, the dependence of the spectral noise density on current, SI(I), differs fundamentally between the cases of the current flowing through the main part of the diode area with a comparatively high barrier and the current flowing through the nanosized patches with a comparatively low barrier.