  This paper reports on the physical and temperature-dependent electrical
characterizations of the oxide/semiconductor interface in MOS capacitors with a
SiO2 layer deposited on 4H-SiC using dichlorosilane and nitrogen-based vapor
precursors. The capacitors, subjected to a standard post deposition annealing
process in N2O, exhibited an interface state density Dit = 9.0 x 1011cm-2eV-1
below the conduction band edge. At room temperature, a barrier height
(conduction band offset) of 2.8 eV was observed, along with the presence of
negative charges in the insulator. The SiO2 insulating properties were
evaluated by studying the experimental temperature-dependence of the gate
current. In particular, the temperature-dependent electrical measurements
showed a negative temperature coefficient of the Fowler-Nordheim electron
barrier height (dFB/dT = - 0.98 meV/{\deg}C), which was very close to the
expected value for an ideal SiO2/4H-SiC system and much lower compared to the
values reported for thermally grown SiO2. This smaller dependence of FB on the
temperature and the increase of the current level with temperature in the
transcharacteristics measured in the relative fabricated MOSFETs represents a
clear advantage of our deposited SiO2 for the operation of MOSFET devices at
high temperatures.
