Tracking ultrafast photocarrier dynamics of CaZrO 3 /KTaO 3 heterostructures under ultraviolet illumination

Abstract The two-dimensional electron gases (2DEGs) at the KTaO 3 -based interface exhibit high sensitivity to ultraviolet illumination. Photocarriers excited by light can effectively increase the Rashba spin-orbit coupling strength and enhance the nonlinear charge transport. However, the understanding of the nonequilibrium photocarrier dynamics remains largely unknown. In this letter, we investigate the ultrafast photocarrier dynamics of 2DEGs at the CaZrO 3 /KTaO 3 interface under 330 nm and 300 nm excitation using femtosecond transient absorption spectroscopy and time-resolved photoluminescence. Our results demonstrate that 300-nm excitation generates high-energy hot electrons, which dissipate rapidly (hundreds of femtoseconds) via optical phonon interactions and reduce effective carrier concentration. In contrast, 330-nm excitation populates electrons near the conduction band minimum, suppressing such scattering process and extending lifetimes to picosecond scale, thereby enhancing carrier concentration. Our work delivers direct insights into optimizing optoelectronic device performance through control of excitation conditions.