Silicon carbide (SiC) is an important semiconductor for the future due to its material properties. The wide energy bandgap of 3 eV allows high temperature operation; the critical field for electric breakdown ten times higher than for silicon promises low loss high voltage switching devices as well as high frequency devices; the chemical inertness and stability opens up possibilities for electronic sensors in harsh environments.
As a test vehicle for SiC electronics the field-effect transistor (FET) has been chosen. The junction-controlled version (JFET) is simple to manufacture but suffers from being a normally-on device. With a metal-oxide-semiconductor gate (MOSFET) the device has low gate leakage but the threshold voltage can be difficult to control. By combining two different gates per device a JMOSFET was demonstrated with constant characteristics up to 300 °C.
Experimental research on SiC devices requires work in three fields: simulation of device operation and thermal losses; manufacture and characterization of devices under various conditions (low and high voltage, extended temperatures); development of process technology (including etching, patterning, doping, electrical contacts, all available at the KTH Electrum lab in Kista).
By combining SiC with other wide bandgap materials and ferroelectric materials novel functionality can be achieved. With PZT (Lead zirconium titanate) in the gate ferroelectric field-effect transistors (FeFETs) with a non-volatile memory effect at temperatures of 200 °C were demonstrated. Schottky, p-n junction and JBS diodes, and bipolar and heterojunction bipolar transistors have been made previously. This is an ongoing project with 9 PhDs since 1993.
Ferroelectrics, High temperature, High voltage, Silicon carbide device technology, Memory devices, Ohmic & Schottky contacts, Heterojunction, Oxidation