A Comparison Between the Diffusion Model and the Combined Diffusion-Thermionic-Emission Model for MS-Junctions by Two-Carrier Numerical Computations

The diffusion model and the combined thermionic-emission-diffusion model for metal-semiconductor junctions have been used in combination with a modified Gummel-De Mari algorithm to obtain one-dimensional, numerical two-carrier solutions, for silicon Schottky diode structures. Solutions for some diode functions vs. voltage, current density, generation-recombination current injection ratio, minority carrier injection ratio, stored charge, and differential capacitance were obtained. For some applied voltages some diode functions vs. positions were calculated: the band diagram including the quasi-Fermi levels, electron and hole carrier density, the total hole current density, the hole drift current density, the electron drift current density and the net charge density. The parameters that have been varied are the barrier height, the carrier life-times, the doping concentration and the length of the diode structure. The results have been compared to and correlate with previous investigations by Vaitkus and Green & Shewchun. A comparison between the diffusion and the combined diffusion-thermionic emission model have been done. Standard methods for determining structure parameters as the 1n I vs. V plot, the Norde plot and the 1/ C 2 vs. V plot have been applied to the numerical results. From this plot the ideality factor, series resistance, barrier height, doping concentration have been determined and the results have been compared to the originally given parameters. The various models result in significant differences (a) on barrier height dependence of injected minority carrier current density, and (b) on the differential resistance at zero bias voltage. The results have also been compared with fabricated silicide and silicon Schottky diodes.