A rapid melt growth process for forming interband n+p+ Esaki tunnel junctions on Ge is shown. The process uses a phosphorus spin-on diffusant and rapid thermal annealing to form the n+ side of the junction, while for the p+ side, a deposited aluminum film serves both as an acceptor dopant source and a melt for epitaxial regrowth of p+ Ge. The current density in these junctions depends strongly on the peak temperature of the Al-Ge melt and ranges between a few mu A/mu m(2) to over 1 mA/mu m(2). The use of a silicon nitride microcrucible improves the surface morphology by confining the melt. Record forward peak current density of 1.2 mA/mu m(2) and reverse interband tunnel current density of 3.8 mA/mu m(2) is achieved at a peak temperature of approximately 600 degrees C. (c) 2007 The Electrochemical Study.