A Tem Study of Rhodium on Gaas; Reactions and Morphology

Abstract

Reaction between Rhodium films and n-type GaAs in the temperature range of 300° to 700°C has been examined using the TEM to look at the interface and phases present. The reaction between Rh and GaAs produces a layered structure of Rh/RhGa/RhAs2/GaAs based on RBS and TEM. Above 300°C, the RhGa phase has an orientation relationship of [011]RhGa // [100]GaAs. In cross-section, an interpenetrated layered structure was observed with equiaxed RhGa above columnar grains of RhAs2. Rhodium is the moving species as suggested by voids at the Rh/reacted layer interface. The interface between the reacted layer and GaAs was smooth at 450° and 20 minutes of annealing but showed 10 nm periodic penetrations when annealed at 400° for 90 minutes. Interface roughness may influence the low barrier height reported for the Rh Schottky diode annealed at 400°.