CHARACTERISTICS OF P-TYPE PTSI SCHOTTKY DIODES UNDER REVERSE BIAS

The characteristics of p-type PtSi Schottky diodes are determined under reverse bias at cryogenic temperatures. Zero-bias and flat-band barrier heights of 0.242 and 0.263 eV, respectively, are evaluated from the data. In addition, the observed lack of excess barrier lowering (other than the image force lowering) is discussed. This excess barrier lowering has previously been postulated to arise from the penetration of the tail end of the metal wave function into the midgap of the semiconductor. Reverse activation analysis is reported for 30 Schottky diodes and an average experimental effective Richardson constant of 45 A/cm2K2 is determined. The difference from the theoretical value (32 A/cm2K2) is attributed to the temperature coefficient of the barrier height. A value of 2.7×10 -5 eV/K for this coefficient is obtained, which is at least one order of magnitude smaller than the variation of the bandgap of silicon. This provides further evidence that the barrier of the p-type PtSi Schottky diode is pinned at the valence-band edge, in agreement with previous results and the expectation inferred from the n-type measurements.