REACTIONS OF VACUUM-DEPOSITED THIN SCHOTTKY-BARRIER METALLIZATIONS ON GALLIUM-ARSENIDE

A series of metals (namely Pt, Ni, Al, Cr, Ti, Ta, Mo, and W) were considered and investigated metallurgically as possible candidates for Schottky barrier metals for high-power GaAs IMPATT diode and FET applications. Interdiffusion, compound formation, lack of adhesion, and stability against humid and oxidizing atmospheres were studied in the temperature range of 250 degree -550 degree C using Rutherford backscattering of 2. 0-2. 25-MeV helium ions, secondary ion mass spectrometry (CAMECA IMS 300), and scanning electron microscopy with energy-dispersive x-ray analysis facility. In this paper we discuss the results and attempt to classify the metals qualitatively into four groups according to the main degradation mechanisms which are likely to limit their use as a Schottky barrier at high operating temperatures.