Effect of surface treatments on ALD Al2O3/4H-SiC metal–oxide–semiconductor field-effect transistors

Silicon carbide (4H) based metal–oxide–semiconductor field-effect transistors provide capabilities in high power and high temperature inaccessible to silicon. However, the performance of thermally grown oxide-based devices remains limited by oxide/semiconductor interface defects. This research employs deposited dielectrics, Al2O3, rather than thermal oxidation. Investigation of various pre-deposition processes reveals different degrees of improvements in the electronic properties. An optimum structure employs the preparation of a nitrided surface via NO annealing, a process known to passivate surface defects, a hydrogen exposure, followed by Al2O3 deposition. Inversion layer field-effect mobilities as high as 52 cm2/V s are reported in the optimum structures. Capacitance–voltage measurements and field-effect mobility characteristics indicate a trapping limited conductivity in Al2O3/4H-SiC inversion channels similar to SiO2/4H-SiC. Leakage currents and interface breakdown are also reported for various Al2O3/4H-SiC MOS structures.