Remote plasma-enhanced atomic layer deposition of gallium oxide thin films with NH 3 plasma pretreatment

High quality gallium oxide (Ga 2 O 3 ) thin films are deposited by remote plasma-enhanced atomic layer deposition (RPEALD) with trimethylgallium (TMG) and oxygen plasma as precursors. By introducing in-situ NH 3 plasma pretreatment on the substrates, the deposition rate of Ga 2 O 3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 A/cycle at 250 °C, respectively. The increasing of deposition rate is attributed to more hydroxyls (–OH) generated on the substrate surfaces after NH 3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga 2 O 3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga 2 O 3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.