The effect of the metallurgical properties of the In-GaAs interface on the electrical properties of ohmic contacts to GaAs

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The electrical properties of Al/In ohmic contacts to GaAs are correlated with the metallurgical properties of the In-GaAs interface. These contacts are formed by the deposition of 300 Å of indium and 1000 Å of aluminium onto n-type GaAs (Nd = 5 × 1017 cm-3) substrates by evaporation in an ultrahigh vacuum system. The non-linear current-voltage characteristics became linear and the resistance dropped by four orders of magnitude after annealing at 200 °C. The forward and reverse current-voltage characteristics are explained by the tunnel emission model. Auger depth profile studies indicated the presence of excess indium and gallium at the In-GaAs interface in annealed samples. Scanning electron microscope studies showed the growth of GaAs spikes just below the indium layer only in annealed samples. The excess indium in the regrown crystals of GaAs is believed to form the heavily doped layer resulting in an ohmic contact. © 1982.

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Thin Solid Films