Temperature-dependent Fowler-Nordheim electron barrier height in SiO2/4H-SiC MOS capacitors

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 × 1011 cm−2 eV−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 (dΦB/dT = − 0.98 meV/°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 ΦB 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.