Laser-chemical vapor deposition of W Schottky contacts on GaAs using $WF6$ and $SiH4$

Tungsten was deposited on GaAs using a low-temperature laser-chemical vapor deposition process. A KrF excimer laser beam incident perpendicularly on a GaAs surface was found to induce metallic W formation from a gas mixture containing $WF6$ and $SiH4$ at laser energy densities as low as $25 mJ/cm2.$ In-situ x-ray photoelectron spectroscopy analysis shows that $SiH4$ plays an important role in the initiation of metallic W deposition at such low laser energy densities. Scanning electron microscopy of the W films shows a dense and regular columnar structure. Auger depth profiles show that the deposited W is pure. No impurities such as F, C, or O were observed, with a detection limit of 1 at. %, and the interdiffusion between W and GaAs is minimal. X-ray diffraction shows that the W film is mostly in the stable, highly conductive α phase, as confirmed by the low resistivity value of $21 μΩ cm.$ Metallic W features of 60 μm on GaAs were obtained by laser direct-projection patterning. $I–V$ measurements show that the W–GaAs structures formed provide good quality Schottky contacts, with an average barrier height of 0.71 eV and an average ideality factor of 1.2. To our knowledge, these are the first Schottky diodes obtained using a laser based resistless projection patterning process on GaAs.