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.