Contact metallurgy optimization for ohmic contacts to InP

AuGeNi and AuZnNi metallizations to n- and p-InP were studied as a function of the annealing temperature in a Rapid Thermal Annealing (RTA) system. For n-InP (S:8×10¹⁸cm^-3) a broad minimum existed from 385°C to 500°C, in which the specific contact resistance, rc, was about 10^-7 ¿cm². The lowest value of 7×10^-8 ¿cm² for n-InP occurred after RTA for 20 sec. at 450°C. For p-InP (Zn:5×10¹⁸ cm^-3) the lowest value of rc, 7×10^-6 ¿cm², was obtained for AuZn without any Ni. Metallurgical investigations indicated, that low rc values were associated with interfacial reactions and the formation of stable barrier-lowering metal-phosphides.