We report a sharp reduction in the resistivity of Ohmic contacts using in situ deposition of molybdenum (Mo) contacts onto n-type In_(0.53)Ga_(0.47)As grown on InP. The contacts were formed by evaporating Mo onto the wafer using an electron beam evaporator connected to a molecular beam epitaxy chamber under ultrahigh vacuum. Transmission line measurements showed specific contact resistivities of 0.5 ± 0.3 Ω μm~2 (2.90 Ω μm), 0.9 ± 0.4 Ω μm~2 (4.3Ω μm), and 1.3 ± 0.4 Ω μm~2 (4.7Ω μm) for Mo on abrupt InAs/InGaAs heterojunctions, graded InAs/ InGaAs, and InGaAs films, respectively. These low resistances meet the requirements for terahertz transistors.
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