Ex situ Ohmic contacts to n-InGaAs

Abstract

The authors report ultralow specific contact resistivity (ρc) in ex situ Ohmic contacts to n-type In0.53Ga0.47As (100) layers, with an electron concentration of 5×1019 cm−3. They present the ρc 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 ρc 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±0.9)×10−8 Ω cm2 for the Mo/In0.53Ga0.47As interface. This ρc is equivalent to that obtained with in situ Mo contacts [ρc=(1.1±0.6)×10−8 Ω cm2]. Ex situ contacts prepared by UV-ozone exposure plus dilute HCl (without any atomic H exposure) result in ρc=(1.5±1.0)×10−8 Ω cm2.