REDUCTION OF LEAKAGE CURRENTS IN SILICON MESA DEVICES

Easily and rapidly manufacturable silicon mesa devices suffer from add itional leakage currents from the mesa rim where np junctions are expo sed to the surface. A modified mesa structure is proposed, which reduc es the drawbacks of leakage currents. The structure contains a metalli zation smaller than the mesa and a very thin (10-nm) contact layer as, for instance, can be grown by molecular beam epitaxy (MBE), The curre nt distribution for a forward-biased junction is given. For cylindrica l symmetry, it was possible to derive analytical solutions. At high cu rrent densities, the voltages at the mesa edge are effectively reduced and the current contribution of the outer part is only a small fracti on of the total current. Numerical examples are given for large test s tructures as used for microwave IMPATT diodes.