Schottky enhancement of contacts to $n-GaAs$ via the exchange mechanism using $NiAlxGa1−x$ as a metallization Available to Purchase

Based on the thermodynamic/kinetic model of the exchange mechanism, the ternary intermetallic compound $NiAlxGa1−x$ (where $0<x⩽1)$ was identified as a metallization that may be used to fabricate Schottky enhanced contacts to $n-GaAs.$ Experimental phase equilibrium studies of the quaternary Al-Ga-Ni-As system, in conjunction with diffusion data available in the literature, indicated that the phase $NiAlxGa1−x$ fulfills the thermodynamic and kinetic requirements necessary for participation in an exchange reaction with GaAs. Contacts to $n-GaAs$ were fabricated by sputter deposition of $NiAlxGa1−x$ metallizations, with compositions corresponding to $x=0.00,$ 0.25, 0.50, 0.75 and 1.00. These contacts were subjected to rapid thermal processing, and analyzed using cross-sectional high resolution transmission electron microscopy and $I-V$ characterization. Electron microscopy and concomitant electron dispersive spectroscopic analysis indicated that a very thin (2.5 nm) interfacial region of $AlxGa1−xAs$ was formed in annealed contacts for which $x>0.00,$ in accordance with the exchange mechanism model. Schottky barrier enhancement was also observed in all annealed contacts for which $x>0.00.$ The degree of Schottky barrier enhancement was shown to be dependent upon the initial composition of the metallization, again in accordance with the prediction of the exchange mechanism model. Schottky barrier heights as high as 0.96 eV were obtained under the optimum annealing conditions of 400 °C for 1 min. However, these experimentally determined Schottky barrier heights were somewhat smaller than the values that were anticipated based upon the exchange mechanism model. Potential reasons for these discrepancies were discussed. Overall, it was demonstrated that the thermodynamic/kinetic model of the exchange mechanism is a powerful tool for identifying metallizations that may be used to enhance the Schottky barriers of contacts to $n-GaAs.$