Quantitative analysis of arsenic losses during the formation of Au(Zn)/p-GaAs ohmic contacts

Abstract

The formation of Au(Zn)/p-GaAs ohmic contacts by furnace annealing either in open or closed configurations with a dielectric cap has been investigated. Evaluation of the extent to which the GaAs substrate decomposes under these conditions was of primary concern. This was studied by measuring the amount of As losses, using the Cr-collector method, and correlating this with the amount of Ga diffused into the Au(Zn) metallization. The thermally induced decomposition of GaAs in contact with Au(Zn) metallization strongly depends on both the application of the capping layer, and on the thickness of the metallization. The loss of As is reduced to 6×1014 atom/cm2 using thin 10 nm Au/10 nm Zn/30 nm Au metallization annealed with a insulating capping layer deposited by sputtering. Electrical measurements indicate that under these conditions good ohmic contacts are obtained. Thus, the contact reaction sufficient to produce good ohmic contacts can be limited to about one monoatomic layer of GaAs.