Temperature dependence and effect of series resistance on the electrical characteristics of a polycrystalline diamond metal-insulator- semiconductor diode

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Abstract
Temperature dependency and the series resistance effect on the electrical characteristics of a polycrystalline diamond‐based (Au/Ti)/undoped‐diamond/doped‐diamond metal‐insulator‐ semiconductor Schottky diode were investigated in a temperature range 25–300 °C. The current‐voltage (I‐V) characteristics of the device show rectifying behavior with the forward bias conduction limited by series resistance. Over the temperature range investigated, the I‐V data confirmed that the conduction mechanism of the diode is controlled by thermionic field emission. Modifying the thermionic field emission equation to include the series resistance model allows the ideality factor and barrier height of the Schottky diode to be calculated. Temperature dependence of the ideality factor and apparent barrier height was determined. By extrapolating the forward saturation current data, the evaluated ideality factor was observed to decrease from 2.4 to 1.1 while the apparent barrier increased linearly from 0.68 to 1.02 eV in the temperature range from 25 to 300 °C. The Richardson plot, ln(I0/T2) vs 103/T, has linear characteristics and indicates a true barrier height of 0.31 eV. Analysis of the temperature‐dependent series resistor measurements indicates a boron doping activation energy of 0.104 eV in the p diamond. The capacitance‐voltage‐frequency measurement confirmed that the measured capacitance varies with applied bias and frequency due to the presence of the Schottky barrier, impurity level, and high series resistance. Capacitance‐frequency measurement at zero bias indicated that the degrading capacitance at high frequency is primarily due to the high series resistance of the bulk polycrystalline diamond.