ELECTRICAL CHARACTERIZATION OF LASER-INDUCED DEPOSITS OF ALUMINUM ON GALLIUM-ARSENIDE

Aluminium lines have been deposited on semi-insulating gallium arsenid e (100) substrates by visible Ar+ laser decomposition of trimethylamin e alane. The aluminium resistivity, measured by a two-point test metho d, has been found to be as low as 6 muOMEGA cm. A grating composed of parallel aluminium lines (20 mum wide, 1000 angstrom thick and spaced 35 mum apart) was written directly with a laser power of 0.8 W and a s canning speed of 50 mum s-1. The induced temperature at the centre of the laser spot was estimated at about 350-degrees-C. A similar grating was evaporated in a ultra-high vacuum chamber equipped with an electr on gun. Prior to deposition of these two gratings, an aluminium back c ontact was evaporated on both substrates. In order to compare the elec trical quality of the Al/GaAs interfaces obtained by both deposition p rocesses, the current--voltage characteristics as a function of temper ature, as well as the photocurrent intensity delivered by the samples under illumination as a function of bias and photon energy, have been measured. The results show that laser deposition can be used to perfor m a full metallization level (few meter connections) comparable in qua lity with conventional ultra-high vacuum evaporated deposits.