EVIDENCE FOR MULTIPLE BARRIER HEIGHTS IN P-TYPE PTSI SCHOTTKY-BARRIER DIODES FROM I-V-T AND PHOTORESPONSE MEASUREMENTS

Current-voltage-temperature (I-V-T) characteristics of p-type moderately doped PtSi Schottky barrier diodes have been measured as a function of temperature from 77 to 120 K. From thermionic emission theory, the saturation current at each temperature is plotted against inverse temperature. According to this theory, the slope should give the barrier height. However, the experimental data obtained do not correlate well with a straight line relationship. These effects are explained by introducing a model in which there is a range of barriers with a normal distribution. A mean barrier of 0.242 eV with a standard deviation of σ = 0.011 eV is obtained. Photoresponse measurements have also been performed at a temperature of 78.0 K to verify the I-V-T results and to test the distributed model. It is found that the cut-off wavelength for PtSi Schottky diodes is well beyond that predicted by a single barrier, giving further evidence for multiple barriers. To test the distributed model, the parameter extracted from the model, i.e. the spread of the barrier, σ is introduced into the photoemission model. The photoyield thereby calculated compares well with experimental results. © 1990.