Atomic Layer Deposition of InN Using Trimethylindium and Ammonia Plasma

InN is a low band gap, high electron mobility semiconductor material of interest to optoelectronics and telecommunication. Such applications require the deposition of uniform crystalline InN thin films on large area substrates, with deposition temperatures compatible with this temperature-sensitive material. As conventional chemical vapor deposition (CVD) struggles with the low temperature tolerated by the InN crystal, we hypothesize that a time-resolved, surface-controlled CVD route could offer a way

forward for InN thin film deposition. In this work, we report atomic layer deposition of crystalline, wurtzite InN thin films using trimethylindium and ammonia plasma on Si (100). We found a narrow ALD window of 240–260 °C with a deposition rate of 0.36 Å/cycle and that the flow of ammonia into the plasma is an important parameter for the crystalline quality of the film. X-ray photoelectron spectroscopy measurements shows nearly stoichiometric InN with low carbon level (< 1 atomic %) and oxygen level (< 5 atomic %) in the film bulk. The low carbon level is attributed to a favorable surface chemistry enabled by the NH₃ plasma. The film bulk oxygen content is attributed to oxidation upon exposure to air via grain boundary diffusion and possibly by formation of oxygen containing species in the plasma discharge.