THE INTERACTIONS BETWEEN SI/CO FILMS AND GAAS(001) SUBSTRATES

Abstract

Interfacial reactions of Si/Co films on (001) oriented GaAs substrate, in the temperature range 300-700 degrees C for 30 min, have been investigated using a combination of x-ray diffraction, Auger electron spectroscopy, and transmission electron microscopy. Cobalt starts to react with GaAs and Si at 380 degrees C by formation of Co2GaAs, and Co2Si phases, respectively. At 420 degrees C, the entire layer of Co is consumed, and the layer structure is observed with the sequence Si/CoSi/ CoGa(CoAs)/Co2GaAs/GaAs. Contacts produced in this annealing regime are rectifying and the Schottky barrier heights increase from 0.69 eV(as-deposited state) up to 0.81 eV (420 degrees C). In the subsequent reaction, CoSi grows at the expense of the decompositions of CoGa and CoAs at 460 degrees C. In addition, the ternary phase also is decomposed and only the CoSi phase remains upon the GaAs surface at 600 degrees C. Contacts produced at higher temperature regime (>460 degrees C) have low barriers. The interface between CoSi and GaAs is stable up to 700 degrees C. The results of interfacial reactions can be understood from the calculated Si-Co-Ga-As quaternary phase diagram.