Ultrafast carrier dynamics in type-II ZnO-SnO heterostructure thin films

Abstract

We investigate the carrier relaxation and charge transfer dynamics in type-II ZnO-SnO heterojunction thin films using wavelength-dependent femtosecond transient absorption measurements. Under SnO-selective excitation conditions, absorption signals related to ZnO are observed on a subpicosecond time scale, which indicates ultrafast electron transfer from SnO to ZnO. The spatial separation of electrons and holes across the ZnO-SnO interface leads to a long-lived carrier decay process with a lifetime of ∼4 ns, 2 times longer than resonant excitation of both ZnO and SnO in the heterostructures. Our results provide a framework for understanding the photophysics of tin oxide semiconductor heterostructures.

Ultrafast Nonlinear Optical Response and Carrier Dynamics in Layered Gallium Sulfide (GaS) Single-Crystalline Thin Films

“…The fast and slow decay components could be attributed to the defect trapping and inter-band carrier recombination in β-GaS thin films, respectively. These results are analogous to that reported for other semiconductor materials (Fang et al, 2016;Li et al, 2017;Kong et al, 2018;Yan et al, 2020;Li et al, 2021).…”

“…The TA signal remains almost constant from 0 to 10 ps, followed by an exponential decay. To analyze the TA results, we used the multi-exponential decay model (Li et al, 2017):…”

Ultrafast Carrier Dynamics of Amorphous Zinc Tin Oxide Graded Thin Films

“…24 These results are analogous to that reported for other AOS materials. 25,26,29,30 For 425 nm excitation, the photocarriers are generated by interband transition from a mixed state induced by Sn and O orbital hybridization to CB. 43 Then, the photocarriers share the same recombination pathways as 350 nm pump, which explains the slight dependence of decay dynamics on pump wavelength.…”

“…The time resolution of the TA measurement system was ∼280 fs. Details of our TA measurement can be found in a previous report …”

“…A detailed understanding of the carrier dynamics in semiconductor is extremely useful for the development of future optoelectronic systems. Ultrafast optical spectroscopy is a versatile technique to investigate the dynamic process and the corresponding relaxation mechanism of semiconductors. − Despite some effects, however, the carrier dynamics of ZTO are rarely addressed. , Due to the limited experimental data, the intrinsic carrier recombination mechanism following photon absorption in ZTO remains elusive and needs full discernment.…”