Characterization of Power MESFETs on 4h-SiC Conductive and Semi-Insulating Wafers

We report on the characterization of MESFETs designed for L- and S-band power amplification and processed on 4H-SiC conductive and semi-insulating wafers. Both exhibit promising dc characteristics (I(dss) = 300mA/mm; BV(ds) is greater than 150 V). As expected, the microwave small signal performance is much better on semi-insulating substrates than on conductive ones. For devices on semi-insulating substrates, the drain current continuously decreases with time under dc bias conditions. As a consequence, the RF high-power performance is still modest, and even lower than on conductive substrates. Traps, whose location in the bandgap is not clearly identified yet are probably responsible for this phenomenon. High-temperature I(V) and storage characterization of MESFETs processed on conductive substrates have been performed, and they show good behavior under the conditions of the experiments. (Author)