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Amorphous WSi0.45 Metallization for Self-Aligned GaAs MESFETs

Published online by Cambridge University Press:  26 February 2011

Alex Lahav
Alex Lahav*
Affiliation:
AT&T Bell Laboratories, Reading PA, 19612
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Abstract

Crystallization temperature (Tc) of amorphous WSix films on GaAs was studied as a function of the Si/W ratio. The highest Tc of 875°C for a 20 min anneal was obtained for co-sputtered WSMi films with the Si/W ratio of 0.45 (31 at.% Si). The WSi0.45 films remained amorphous following implant activation anneal and served as a barrier to Ga and As outdiffusion. Pitting of GaAs under the contact was also prevented. The WSi0.45 composition corresponds to the eutectic point between the W and W5Si3 phases, which was explained by the strong glass-forming tendency of eutectic alloys. Amorpous WSi0.45 films formed stable Schottky contacts to n-GaAs and produced minimum reduction of carrier concentration in the substrate. Therefore, the Si/W ratio of 0.45 is suggested as optimal for the WSix refractory gate metallization in self-aligned GaAs MESFErs.

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