Fabrication of ohmic contact based on platinum to p-type compositionally graded AlGaAs layers

Novel metallization scheme was proposed for ohmic contact formation to compositionally graded p-type AlGaAs. A metal multilayers of Ti/Pt/Au, Pt/Ti/Pt/Au and Pt/Ti/Ni/Au were deposited by thermal evaporation using electron gun and resistance heater. The contacts were sequentially annealed by rapid thermall annealing system in N2 atmosphere at various temperatures (in the range from 350°C to 550°C). The duration of annealing step was 2 minutes. The as-deposited Pt/Ti/Pt/Au and Pt/Ti/Ni/Au multilayer metallizations had resistivities of 1.4·10-5 Ω·cm2 which have been gradually deteriorated after each subsequent annealing. The current-voltage characteristics of the ohmic contacts to compositionally graded p-type AlGaAs epitaxial layers were studied and discussed.