Ohmic contacts to III V compound semiconductors: A review of fabrication techniques

Abstract After a brief introduction on the phenomena governing the ohmic contact formation and measurements in metal—semiconductor structures, we present a review of papers on the ohmic contact realization onto III–V compounds. We discuss the thermal behaviour of various multicomponent metal—semiconductor systems (alloying, sintering, use of lasers and electron beams) and comment about overdoping the semiconductor surface before metal deposition (diffusion, ion implantation, epitaxy). We show that, in a general way, the metal III–V semiconductor interactions lead to the formation of compounds. From an electrical point of view, it seems that the main consequence of the compounds appearance is not a large change of the barrier height due to a change of the interface chemistry but the rough interface resulting from particle precipitation. We conclude that, if contacts made up to now, are often simple and usable, they are still far from ideal.