Ultralow resistance in situ Ohmic contacts to InGaAs/InP

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 Omega mu m(2) (2.90 Omega mu m), 0.9 +/- 0.4 Omega mu m(2) (4.3 Omega mu m), and 1.3 +/- 0.4 Omega mu m(2) (4.7 Omega mu m) for Mo on abrupt InAs/InGaAs heterojunctions, graded InAs/InGaAs, and InGaAs films, respectively. These low resistances meet the requirements for terahertz transistors.