Barrier height modification of metal/germanium Schottky diodes

Germanium is experiencing a resurgence of interest due to superior intrinsic properties and recently overcome technological limitations. This paper addresses the problem of Schottky barrier height control. The Fermi level of metal/Ge contacts is pinned at between 0.54 and 0.61 eV below the conduction-band edge, independent of the contacting metallization. We compare the modulation of effective barrier height by means of shallow ion implantation, epitaxial growth, and diffusion from a doped level to create a thin, highly doped interfacial region. Lowering of n-type contacts from 0.54 to 0.4 eV, at room temperature, and enhancement of p-type contacts from 0.09 to 0.23 eV, at 77 K, have been achieved. Experimental results are compared to computer model calculations.