FABRICATION AND RESISTANCE EVALUATION OF METAL OHMIC CONTACTS TO GaAs

Abstract

GaAs technology has attracted much attention in the last twenty five years or so because of its wide and potential appli-cations in many optical and microwave devices. Various metals have been used to form ohmic contacts with GaAs. In the present work, we used Aluminum metal for the formation of ohmic contacts to n—GaAs using a vacuum evaporating system. These contacts were alloyed in a standard furnace. We obtained linear current—voltage characteristics, which show the ohmic behaviour of contacts. It has been shown that the contact resistance is a function of the contact diameter. The specific contact resistance was also calcul-ated and found to be of the order of 2.2 x 10-211 — cm2, which was in good agreement with value obtained by Cox and Strack (1967). Apart from electrical characterization of ohmic contacts, the structural characterization of contact was also done. X—Ray diffractometer was used in finding the lattice constant for GaAs sample and GaAs alloyed with Aluminum. SEM was used to take photographs and for measuring the contact diameters. The temperature profile of the furnace was also measured at different temperatures.