The Interfacial Reactions, Phase Equilibria and Electrical Properties of Co/GaAs System

Interfacial reactions, phase equilibria and elecrrical properties of Co films on (001) oreinted GaAs substrate, in the temperature range 300- for 30min. have been investigated using x-ray diffraction and Augger electron spectropcopy. Cobalt started to react with GaAs at 38 by formation of CoGaAs phase. At 42, CoGa and CpAs nucleated at the Co and CoGaAs interface and grew with CoGaAs upto 46. contacts produced in this annealing regime were rectifying and Schottky varrier heights increased from 0.688eV(as-deposite state) up to 0.72eV(42). In the subsequent reation, the ternary phase started to decompose and lost stoichiometry at 50. At higher temperature, CoGaAs disappered and CoGa/CoAs/GaAs layer structures were formed. Contacts produced at higher temperature regime(>50) showed very low effective barriers. The results of interfacial reactions can be understood from the Co-Ga-As ternary phase diagram.