Growth and Characterization of Epitaxial InN Films on Sapphire Substrate using an ArF Excimer Laser-Assisted Metalorganic Vapor-Phase Epitaxy (LA-MOVPE)

Abstract

Epitaxial InN films have been grown on sapphire substrate by using an ArF excimer laser-assisted metalorganic vapor-phase epitaxy (LA-MOVPE) as a new potential growth technique. An ArF excimer laser photolytically dissociates NH3 with independent of the growth temperature while photolytical dissociation of trimethylindium (TMI) is not observed. The photolytically dissociated NH3 reacts with TMI to deposit InN film and even single crystalline film is grown. This enables InN film deposition over a wide range of growth temperature, from a room temperature to a very high temperature (700°C). Single crystalline InN films with smooth surfaces are successfully grown in the temperature range of 350-700°C with a variety of condition. The characterization of the InN films grown over a wide range of temperature and condition enables to find out some important evidences about the InN properties, especially the band gap energy. Interestingly, this new growth technique provides a growth rate of more than 0.5 µm/h just by flowing a very little amount (∼100 sccm) of NH3. While to obtain such growth rate in our conventional MOVPE a total amount of ∼6000 sccm NH3 gas is required. The electrical properties are still found to be poor compared to the recently reported good results. Important evidences as to what species is responsible for poor electrical properties in the grown InN are discussed.