Ultrafast Spectroscopy and Red Emission from β-Ga(2)O(3)/β-Ga(2)S(3) Nanowires

Ultrafast pump-probe and transient photoluminescence spectroscopy were used to investigate carrier dynamics in β-Ga(2)O(3) nanowires converted to β-Ga(2)O(3)/Ga(2)S(3) under H(2)S between 400 to 600 °C. The β-Ga(2)O(3) nanowires exhibited broad blue emission with a lifetime of 2.4 ns which was strongly suppressed after processing at 500–600 °C giving rise to red emission centered at 680 nm with a lifetime of 19 μs. 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 β-Ga(2)O(3)/Ga(2)S(3) nanowires processed at 500 to 600 °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 Ga(2)S(3).