Influence of the synthesis conditions on gallium sulfide thin films prepared by modulated flux deposition

Gallium sulfide thin films were deposited on soda-lime glass substrates by Modulated Flux Deposition (MFD). Using a low deposition rate (1 angstrom s(-1)), 100 nm thick layers were prepared at temperatures ranging from 450 to 150 degrees C with a variable supply of elemental sulfur. EDX analysis showed that these films approached the MX stoichiometry; they corresponded to sulfur-deficient GaS. By raising the availability of sulfur, the bandgap energy (E(g)) was increased from 3.2 to 3.6 eV at 350 degrees C, while it remained constant (similar to 3.6 eV) at 150 degrees C; these high Eg values were mainly attributed to quantum size effects. Therefore, high-transmission GaS thin layers can be prepared at only 150 degrees C by MFD.