INTERFACIAL REACTIONS IN THE TI GAAS SYSTEM

The reaction between thin Ti films and GaAs, in the temperature range 300-600 °C, was studied using a combination of Auger electron spectroscopy, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy, and electrical measurements. Titanium starts to react with GaAs at ∼ 400 °C, producing a layered Ti/Tix Ga1 - x /TiAs/GaAs microstructure. The reaction sequence suggests that Ti diffuses into the GaAs and liberates Ga while forming TiAs. Kinetic studies show that the reaction is diffusion controlled with an activation energy of 1.75 ± 0.05 eV. The reaction products, for fully reacted films, were identified from electron diffraction patterns as a NiP-type TiAs phase and TixGa 1-x (hexagonal structure: a = 0.569 nm, c - 0.932 nm, x = 0.35 ± 0.05). Correlation of electrical measurements with TEM results indicates that the formation of TiAs at the interface coincides with an increase in barrier height (0.84 eV) over the as-deposited value (0.72 eV). © 1988 American Vacuum Society.