BARRIER HEIGHTS OF GAN SCHOTTKY CONTACTS

Silver and lead contacts prepared by evaporation onto clean n-GaN(0001 ) surfaces are rectifying. Their zero-bias barrier heights and idealit y factors were determined from the current-voltage characteristics. Th e observed linear correlation between the barrier heights and the idea lity factors is attributed to nonuniform distributions of barrier heig hts along the interfaces, The barrier heights of ideal Schottky contac ts depend on the applied voltage due to the image-force lowering only and their ideally factors n(if) are approximately 1.01. By extrapolati on of our experimental data to ii = 1.01. we obtain barrier heights of 0.82 eV and 0.73 eV for uniform Ag- and Pb/n-GaN(0001) contacts, resp ectively. By applying the idea of metal-induced gap states (MIGS), the barrier heights of ideal Schottky contacts have been predicted to var y linearly as a function of the difference of the metal and the semico nductor electronegativities. The zero-charge-transfer barrier height a nd slope parameter are characteristic of the respective semiconductor. The zero-charge-transfer barrier heights have been calculated using a n empirical tight-binding approach and the slope parameters are given by the optical dielectric constants. The experimental barrier heights of GaN Schottky contacts confirm the predictions of the MIGS-and-elect ronegativity model.