Electrical studies on cubic boron nitride MIS structures

A systematic investigation of the electrical properties of Metal-cBN-p-Silicon MIS structures through Capacitance-Voltage and Leakage Current measurements was undertaken. Electrical leakage measurements were performed using an HP4145B Semiconductor Parameter Analyzer and Capacitance-Voltage results were obtained using an LCZ Meter.; Poole-Frenkel conduction was observed to be dominant in cBN MIS structures at low electric fields. Trap height values obtained for the films were ∼0.8 eV. Schottky conduction was observed to be the dominant conduction in predominantly cBN MIS structures. The gold-cBN barrier height was obtained to be ∼0.6 eV. For a fraction of MIS structures incorporating indium gate metal, Poole-Frenkel and Schottky conduction was observed. For other contacts evidence was observed of the alloying of indium with cBN resulting in Ohmic-like behavior analogous to the behavior of indium with GaAs. Evidence of the pinning of the Fermi level at the Metal-Insulator interface was obtained from the similarity of the gold-cBN and indium-cBN barrier heights. MIS structures incorporating tBN as the insulating layer exhibited similar conduction behavior to the cBN MIS structures. The gold-tBN barrier height obtained was ∼0.68 eV and the trap height obtained was ∼0.86 eV.; A correlation between leakage current and RMS roughness of the surface was observed providing evidence of roughness mediated field enhancement at the metal insulator interface resulting in higher leakage currents. Leakage current of the cBN MIS structures at high electric fields exhibit a similar functional relationship to post Soft Breakdown I-V curves of ultrathin oxides at high electric fields. Hard Breakdown was not observed for our films at fields up to 2 MV/cm. This sets a lower bound for the breakdown field for our BN films. Resistivity values in the range 109 O-cm to 1012 O-cm were obtained for cBN and tBN films.; To our knowledge, we obtained the first Capacitance-Voltage results on BN MIS structures with a cBN phase close to 100% and with silicon as the semiconductor material. No hysteresis was observed in the C-V curve when the voltage was swept from accumulation to inversion and back to accumulation. A small shift in VFB was observed and negative fixed nitride charge density of 5x1011 cm-2 was determined. High Dit values were obtained for the cBN films compared to hBN films reported in the literature indicating that the cBN nucleation process is accompanied with significant trap creation similar to our leakage results on cBN MIS structures.