Correlation between solid-state reaction and electrical properties of the Rh/GaAs Schottky contact

The solid-state reactions between (100) GaAs substrates and Rh films ∼150 Å and ∼600 Å thick, annealed at temperatures between 300 and 800°C, are investigated with conventional and heavy ion Rutherford backscattering spectrometry, and x-ray diffraction. Initiation of interface reactions between the Rh films and the GaAs substrate is observed at ∼300°C. Laterally segregated RhGa, RhAs, and RhAs₂ phases are detected for the 150-Å Rh/GaAs contact annealed in the temperature range of 300-700°C. For thick Rh film (∼600 Å) on GaAs, vertical phase separation between the RhGa and the Rh-As phases is observed after annealing. After annealing at 700°C for 20 min, the reaction between the 600-Å Rh film and GaAs is complete and a layer sequence of RhGa/RhAs₂/GaAs results. Electrical properties of Rh/n-GaAs diodes are measured using the current voltage dependence. A correlation between the electrical behavior and the metallurgical reaction is observed.