Ultrafast Spectroscopy and Red Emission from beta-Ga2O3/beta-Ga2S3 Nanowires

Abstract

Ultrafast pump-probe and transient photoluminescence spectroscopy were used to investigate carrier dynamics in beta-Ga2O3 nanowires converted to beta-Ga2O3/Ga2S3 under H2S between 400 to 600 degrees C. The beta-Ga2O3 nanowires exhibited broad blue emission with a lifetime of 2.4 ns which was strongly suppressed after processing at 500-600 degrees C giving rise to red emission centered at 680 nm with a lifetime of 19 mu s. Differential absorption spectroscopy reveals that state filling occurs in states located below the conduction band edge before sulfurization, but free carrier absorption is dominant in the beta-Ga2O3/Ga2S3 nanowires processed at 500 to 600 degrees C for probing wavelengths >500 nm related to secondary excitation of the photo-generated carriers from the mid-gap states into the conduction band of Ga2S3.