Unraveling the Thickness-Dependent High Photoconductivity in BaSnO3 Thin Films: Insights from Ultrafast Charge Carrier Dynamics

Abstract Barium stannate, a perovskite-structured semiconductor, is gaining significant attention for its potential in high-performance UV photodetectors and optoelectronic applications. This study investigated the photo-response of epitaxial BaSnO3 (BSO) thin films grown using pulsed laser deposition. Our findings revealed an exceptionally high photo-response in BSO films having thicknesses (90, 270, and 360 nm). Detailed optical analyses were conducted to elucidate the photoconductive response's mechanisms, including photoluminescence, time-resolved photoluminescence, and ultrafast transient spectroscopy. Notably, ultrafast transient spectroscopy was employed for the first time on this material. Leveraging BSO's wide bandgap (3.4 eV), photoconductivity measurements in the UV range showed a peak responsivity of 5 A/W at 5 V with a 360 nm film and a response time of 470 ms. The transient spectroscopy reveals the thickness-dependent carrier dynamics, such as carrier relaxation, carrier trapping in mid-gap states, and recombination. Specifically, observed trapping times were approximately 6 ps for 360 nm thickness, 26 ps for 270 nm thickness, and 59 ps for 90 nm thickness. This research enhances the understanding of the photoconductive behavior of barium stannate thin films and lays the groundwork for optimizing BSO-based UV-sensitive optoelectronic devices.