SiC 4H: May 2018

May 15, 2018

Efficient positron moderation with a commercial 4H-SiC epitaxial layer

We have studied the properties of a commercially available 4H-SiC epitaxial layer and evaluated its potential application as an efficient positron remoderator. A remoderation efficiency of more than 65% has been measured for incident positrons with 1 keV energy. We have determined the work function and the energy distribution of the emitted slow positrons, a property which is essential for practical applications. Comparison of the positron moderation properties of the epitaxial layer with results from a n-type 4H-SiC single crystal, indicate that the epitaxially grown layer is a superior secondary moderator than its substrate counterpart.

Source:IOPscience

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May 7, 2018

Monte Carlo simulation of 4H-SiC IMPATT diodes

A Monte Carlo particle (MCP) bipolar model for 4H-SiC consisting of three electron and two hole bands is developed to simulate the millimetre wave power generation by 4H-SiC IMPATT diodes. Validation of the model is provided by comparing (i) carrier transport properties with full band simulation results and (ii) hole impact ionization coefficients with the most recent experimental results. MCP simulation results are reported for a low-voltage 4H-SiC IMPATT diode connected directly in a parallel resonant circuit with a standard 50 O load resistor. The detailed evolution of carrier generation, accumulation and drift are presented to confirm the design of an efficient hi-lo IMPATT diode structure. Critical performance parameters investigated include bias and frequency dependences of millimetre wave output power, generation efficiency, conduction current and frequency stability at an operating frequency around 200 GHz. It is predicted that very high-power millimetre waves at around 200 GHz can be generated at pulse mode.