THERMAL-STABILITY OF MO-AL SCHOTTKY METALLIZATIONS ON N-GAAS

The contact stability and electrical characteristics of sputtered Mo-Al alloy metallizations (Mo74Al26, Mo27Al73, Mo12Al88) on n-GaAs have been investigated. The contacts were annealed by rapid thermal processing in the temperature range of 500-1000-degrees-C for 20 s. X-ray diffraction, Auger depth profiling, scanning electron microscopy, and transmission electron microscopy (TEM) were used to study the structural characteristics. The Schottky diodes were assessed using the current-voltage measurements. The Mo74Al26/GaAs and Mo27Al73/GaAs contacts were stable up to 900-degrees-C anneal, while interfacial reactions in 800-degrees-C annealed Mo12Al88/GaAs contact were observed. Variations of the film surface morphologies and the degradation of the diodes after annealing can be well correlated to the interfacial stabilities. For all thermally stable Mo-Al/GaAs diodes, the Schottky barrier heights increased with annealing temperature. The AlxGa1-xAs at the interface, which contributes to the enhancement of the barrier height, has been clearly verified by the dark field cross-sectional TEM viewed along the [100] of GaAs.