We investigated the thermally induced solid state interdiffusion of Au/Ge/Pd and Ge/Pd ohmic contacts on MBE grown n-GaSb. Furthermore, the electrical behavior of these contacts for different contact sizes down to 540 nm in diameter was compared. A specific contact resistivity as low as 4.9 x 10(-6)Omega cm(2) was measured for the Au/Ge/Pd metallization. After annealing, polycrystalline AuSb2 was observed by grazing incident X-ray diffraction (GIXD). Compared to Ge/Pd metallizations a gold top layer reduces the specific contact resistivity. The atomic structure or microstructure of the Au;Ge/Pd metallization showed a significant reduction of the thickness of amorphous Ge and led to a more spiky interface, which was observed by cross-sectional transmission electron microscopy (TEM). Furthermore, an epitaxial re growth of GaSb occurs, which is estimated to lead to a n(+)-GaSb layer. The atomic microstructure has a significant effect on the current voltage (I-V) characteristic up to a contact size of 950nm in diameter, which shows a wide spread from ohmic to a more Schottky like behavior.