Schottky Properties of Tungsten Compounds Refractory Contacts on n-GaAs Fabricated by Ion Beam Assisted Deposition

Abstract

A low energy ion beam assisted deposition (IBAD) technique has been developed to fabricate refractory W-Si-N films for the application to gate electrode of GaAs metal-semiconductor field effect transistors( MESFETs ). Thermal stability of the IBAD refractory metal/n-GaAs interface was investigated by examining the microstructure and Schottky diode characteristics. The Schottky barrier heights of 0.71, 0.84, and 0.76 eV were obtained after thermal annealing at 850°C for the W/, WN0.27/, and WSi0.3N0.4/GaAs diodes, respectively, and these values are comparable to those of the best results published with conventional reactive sputtering. While some crystalization of the deposit and reaction between film and substrate at the interface were observed with TEM for the W/ and WN/GaAs contacts annealed at 800°, the WSiN film remained amorphous and showed clear interface with the GaAs substrate without significant morphological change. The WS0.3N0.4/GaAs diode showed good thermal stability of Schottky barrier heights with only 20 meV variation in the temperature range between 700 and 850°C, and that is proposed to be due to the stable microstructure.