Interfacial reactions of Si/Co films on (001) oriented GaAs substrate, in the temperature range 300-700°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°C by formation of Co2GaAs, and Co2Si phases, respectively. At 420°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°C). In the subsequent reaction, CoSi grows at the expense of the decompositions of CoGa and CoAs at 460°C. In addition, the ternary phase also is decomposed and only the CoSi phase remains upon the GaAs surface at 600°C. Contacts produced at higher temperature regime (>460°C) have low barriers. The interface between CoSi and GaAs is stable up to 700°C. The results of interfacial reactions can be understood from the calculated Si-Co-Ga-As quaternary phase diagram.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry