The In-Based Metal Ohmic Contacts to n-GaAs

Abstract

ABSTRACTElectrical, structural and reaction characteristics of In-based ohmic contacts to n-GaAs was studied. Attempts were made to form a low band gap interfacial phase of InGaAs to reduce the barrier height at the metal/semiconductor junction and thus yielding a low resistance, high reliability contacts. The contacts were fabricated by e-beam sputtering Ni, NiIn and Ge targets on VPE grown n+-GaAs film (∼1μm, 2xl018 cm-3) in UHV as the structure of Ni(200Å)/NiIn ( 100Å)/Ge(40Å)/n+-GaAs/SI-GaAs, followed by rapid thermal annealing at various temperatures (500-900 °C). The lowest specific contact resistivity (pc) of (1.5±0.5)xl0-6 Qcm2 measured by transmission line method (TLM) was obtained after annealing at 700 °C for 10s. Auger sputtering depth profile and transmission electron microscopy (TEM) were used to analysis the interfacial microstructure. By correlating the interfacial microstructure to the electronical properties, InxGa1-xAs phases with large fractional 'area grown epitaxilly on the GaAs were found to be essential for reduction of the contact resistance.