The fabrication and characterization of planar, millimetre-wave diodes with in situ/ deposited epitaxial aluminium Schottky contacts is reported. A novel self-aligned technique developed to connect the in situ/ grown epitaxial Al Schottky contacts to the ex situ/ deposited bonding pads is described. The I-V/, noise and thermal characteristics of the epitaxial Al diodes are investigated and compared with those of conventionally made Ti/Pt/Au diodes. The epitaxial Al diodes have better ideality factors, higher barrier heights, higher series resistance and higher breakdown voltages than the Ti/Pt/Au diodes. The junction capacitances are almost the same. The noise figures of the diodes were measured using a single balanced mixer. The epitaxial Al diodes had higher noise than the Ti/Pt/Au diodes. The electrical characteristics of the epitaxial Al diodes were hardly changed (somehow improved) after a high-temperature annealing step, whereas the conventional Ti/Pt/Au diodes were catastrophic failures. The epitaxial Al diodes could have a higher burn-out resistance and a longer life than the conventionally made Ti/Pt/Au diodes.