Stability of TaSix-GaAs Schottky barriers in rapid thermal processing

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Abstract
n‐type GaAs samples coated with TaSi2 and Ta5 Si3 Schottky barrier contacts were heated in a flashlamp rapid thermal processing (RTP) system to temperatures between 600 and 950 °C. We have measured the evaporation of gallium and arsenic through the contact overlayers which results from the decomposition of the GaAs substrate. These decomposition measurements have been correlated with the Schottky barrier behavior as determined from forward‐bias current‐voltage characteristics and selected capacitance‐voltage measurements. The high‐temperature stability against decomposition and electrical degradation was superior for Ta5 Si3 contacts relative to TaSi2 contacts. We observed for both contact compositions that the onset temperature for decomposition of GaAs was slightly lower than the maximum temperature for electrical stability. Thus, we found that in some cases substantial decomposition occurred with no effect on the current‐voltage characteristics. For example, Ta5 Si3 contacts maintained a stable barrier height of 0.78 eV through 10 s RTP treatments up to 900 °C, in spite of decomposition of at least ten equivalent monolayers of GaAs.