Laser photochemical deposition of germanium‐silicon alloy thin films

Thin films of Ge‐Si alloys were deposited by 193 nm photolysis of GeH4/Si2H6 gas mixtures using an ArF laser. For substrate temperatures below 350 °C, deposition occurred only with the laser present, while for temperatures above 400 °C, film growth was little influenced by laser photolysis and resembled conventional chemical vapor deposition (CVD). The Si/Ge ratio in the films was about three times the PSi2H6/PGeH4 ratio of reactant partial pressures for deposition in either the laser photolysis or the CVD regime. This result indicates that there is strong cross chemistry between silicon and germanium‐bearing species in the gas phase. Film stoichiometry was measured by Auger analysis and Raman spectroscopy, with both methods leading to the same film composition.

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