DIFFUSION EFFECTS IN P-TYPE PTSI SCHOTTKY DIODES UNDER REVERSE BIAS

At low temperature, the dominant current transport process of a p-type PtSi Schottky diode on a moderately doped Si substrate is thermionic emission over the barrier. In this paper, current has been measured as a function of temperature at a fixed reverse bias for several Schottky diodes. It is found that diffusion effects due to the limitation upon the diffusion rate through the space-charge region can become significant under some conditions. At moderate field, these conditions are calculated to be at a temperature of 150 K or greater, depending on the doping density of the devices. I-V-T measurements were carried out on several Schottky devices fabricated in slightly different ways, and the diffusion effect was observable in some of these devices. A numerical routine is utilized to fit the experimental data to a combined thermionic emission-diffusion theory in these regions. It is found that the experimental results fit this theory well. In addition, the acceptor density at which diffusion becomes the dominant current at 80 K under moderate field is calculated to be around 5 X 10(11) cm-3.