Ex situ Ohmic contacts to n-InGaAs

The authors report ultralow specific contact resistivity (p(c)) in ex situ Ohmic contacts to n-type In0.53Ga0.47As (100) layers, with an electron concentration of 5 X 10(19) cm(-3). They present the P-c obtained for molybdenum (Mo) contacts to n-type In0.53Ga0.47As, with the semiconductor surface cleaned by atomic H before metal deposition. The authors compare these data with the P-c obtained for contacts made without atomic H cleaning. After exposure to air during normal device processing, the semiconductor surface was prepared by UV-ozone exposure plus a dilute HCl etch and subsequently exposed to thermally cracked H. Mo contact metal was deposited in an electron beam evaporator without breaking vacuum after H cleaning. Transmission line model measurements showed a contact resistivity of (1.1 perpendicular to 0.9) X 10(-8) Omega cm(2) for the Mo/In0.53Ga0.47As interface. This p(c) is equivalent to that obtained with in situ Mo contacts [p(c)=(1.1 perpendicular to 0.6) X 10(-8) Omega cm(2)]. Ex situ contacts prepared by UV-ozone exposure plus dilute HCl (without any atomic H exposure) result in p(c)=(1.5 perpendicular to 1.0) X 10(-8) Omega cm(2). (C) 2010 American Vacuum Society. [DOI:10.1116/1.3454372]