Simulating the Influence of Mobile Ionic Oxide Charge on SiC MOS Bias-Temperature Instability Measurements

We report here on results obtained using a time-dependent drift-diffusion model to simulate ion transport in the gate oxide of a SiC MOS device during bias-temperature instability measurements to assess the impact on threshold voltage under typical testing conditions. Measured threshold voltage is found to depend strongly on the temperature and mobile ion species, which in combination with the measurement parameters determine how the ions react to the stress and measurement sequence. Simulations show that, based on their mobilities, both potassium-like and copper-like ions may be responsible for experimental observations of a negative trend in threshold instability above 100 °C for SiC MOS devices.

LOCAL LATTICE STRUCTURE AND DOPANT OCCUPANCY OF DOPED LITHIUM NIOBATE CRYSTALS

We present a systematic study of the local distortions produced upon doping metal ions to lithium niobate ( LiNbO 3, LN) single crystals. The impurity bond length can be predicted by a radial force constant model, when the dopant ions substitute for Li + or Nb 5+ ions in the LN crystallographic frame. From the viewpoint of constituent chemical bonds, the lattice energy can be described as the function of bond valence on the basis of Born–Haber cycle for the formation of an ionic oxide M m O n . The dopant occupancy in the LN matrix can be determined by comparing the deviation of its lattice energy in different locations at both Li + and Nb 5+ sites, on the basis of the bond length relaxation of impurity ions, which can agree well with the experiment results. The effect of impurity ions on the property modification of LN crystals is also discussed according to our calculated results.