GALLIUM PLUS METAL CONTACTS TO GALLIUM-ARSENIDE ALLOYED IN AN ARSENIC MOLECULAR-BEAM

Several metal contact systems containing gallium were used to study metallurgical and electrical effects by using a molecular arsenic beam during the alloying of n-type epitaxial GaAs layers. In situ voltage-temperature measurements and room and liquid nitrogen temperature current-voltage characteristics were obtained and microscopy studies were carried out. With gold-based contact metal systems containing gallium, smooth and continuous metal layers with an ohmic or rectifying character were generally obtained depending on whether or not the surface of the samples was exposed to an As2 molecular beam during the heat treatment. In contrast, silver-based contact systems containing gallium resulted in discontinuous metal layers, vigorous balling up and a sharp rise in the contact resistance during cooling down. The experimental results are discussed and compared with previous results for vapour phase epitaxy. © 1979.