Electrical characterisation of epitaxial 6H-SiC by admittance spectroscopy

Thermal admittance spectroscopy has been carried out on lightly p type and n type doped Schottky diodes to determine the activation energies of both N and Al in 6H-SiC epitaxial layers. The rather high values found (82 and 137 meV for N, 212 and 248 meV for Al) imply incomplete ionisation of the dopants at room temperature. This must be taken inter account in understanding the electrical properties of 6H-SiC devices as a function of temperature. The temperature mobility law of electrons has been determined from current-voltage measurements on junction field effect transistors and from theoretical calculations of the carrier concentration, assuming a two level structure of the doping impurities. (C) The Institute of Materials.