Study On Growth Of TmFeO₃ Film And Integrated Optoelectronic Devices

Integrated photoelectric transducer has been introduced extensively into the fields of optical communication,sensor,and energy conversion.In the post-Moore era,optoelectronic interconnect chips have developed for multi-function,hybrid integration and high-speed information processing.With increased requirements of these innovative optoelectronics,switchable photovoltaic integrated devices have attracted considerable attentions.Hexagonal rare earth ferrites have been reported with direct bandgap of about2.0 eV,while both ferroelectric and ferromagnetic properties have also been investigated.Planar ferroelectric photovoltaic devices can be prepared to provide an alternative foundation for novel applications.However,intensity of remanent polarization is only about 1/3 of saturated polarization due to the characteristic‘up-up-down'displacement of rare earth ions.The photoelectric applications of single-crystal materials are limited,but electromigration of oxygen-vacancy defects provides another switch method and can induce the pyroelectric effect.Therefore,further studies of hexagonal rare earth ferrites and its integrated optoelectronic devices are valuable.In this paper,to study the structure and photoelectric properties,thulium ferrite?TmFeO₃?films have been grown on Sapphire substrates via pulsed laser deposition method.Characterized by XRD,AFM and Raman spectrometer,TmFeO₃ films show the surface with nanoparticles distribution,and form in a hexagonal structure of the P6₃cm space group above substrate temperature⁷50?.Furthermore,from the results of Ferroelectric Analyzer,UV-Vis-NIR Spectrophotometer and PPMS,oxygen-vacancy defects have existed in TmFeO₃ films,and weakened spontaneous polarization performs,while the calculated band gap is about 2.0 eV.This lays a foundation for preparing and studying integrated optoelectronic devices.The photoelectric conversion of TmFeO₃ films have been elucidated by discussing the results of integrated optoelectronic devices with lateral and vertical cell configurations,separately.In photoconductive devices with lateral structure,photo-generated electron-hole pairs are separated mainly under bias voltage,and no obvious photovoltaic effect can be explained by symmetry of band structure even if oxygen defects drift.The significant decline of responsivities reveal that thermal effect is induced by the exchange of photons and phonons,while carrier concentration is still dominated by the electronic transition between valence band and conduction band.Besides,the switchable photocurrent,correlated to both direction and strength of poling fields,has been observed in photovoltaic devices with a vertical architecture.We find field-switchable built-in potential can be contributed to the formation of high-concentration oxygen-vacancy defects layer in the Schottky barriers.Meanwhile,light-induced pyroelectric effect has shown transient currents enhanced with thermal gradient along out-of-plane direction.Defects distribution can be adjusted again by the transient pyroelectric potential,which eventually results in short-circuit photocurrent reversed or enhanced for the case with power density above¹2 mW/cm².These phenomena provide a feasible solution for designing switchable photo-pyroelectric dual-function integrated devices.