Mesoscopic Free Path of Nonthermalized Photogenerated Carriers in a Ferroelectric Insulator

Abstract

We show how finite-size scaling of bulk photovoltaic effect-generated electric field in epitaxial ferroelectric insulating BaTiO3(001) films and photo-Hall response involving the bulk photovoltaic current reveal large room-temperature mean free path of photogenerated non-thermalized electrons. Experimental determination of mesoscopic ballistic optically generated carrier transport opens a new paradigm for hot electron-based solar energy conversion, and for facile control of ballistic transport distinct from existing low-dimensional semiconductor interfaces, surfaces, layers or other structures.

Shift current in the ferroelectric semiconductor SbSI

“…The absence of the photo-Hall effect and the prefect reversal of photocurrent upon opposite poling support that the ballistic photocurrent 17,31 is not relevant in our observation. Note that the spatial-oscillation of the photocurrent due to the optical birefringence 2 , which may cancel the photo-Hall current, can be ruled out, since we illuminate the sample along one of the crystallographic axes and with the light polarization exactly along the c-axis (E(ω)//c).…”

Light‐Induced Reversible Control of Ferroelectric Polarization in BiFeO3

“…The theoretically unlimited V OC , which easily modifies the refractive index, is also likely to trigger polarization switching in ferroelectrics under illumination. However, the electric field associated with the V OC is either parallel to the ferroelectric polarization or smaller than the coercive field . For instance, the largest reported value of the electric field generated by the V OC in BFO thin films, which is a room‐temperature multiferroics showing substantial BPV effect, is ≈5.5 kV cm −1 that is about two orders of magnitude smaller than the coercive field .…”

Nanoscale excitonic photovoltaic mechanism in ferroelectric BiFeO3 thin films

“…The theory is termed the bulk photovoltaic effect (BPE) 3 with above bandgap photovoltage and an associated shift current effect. [5][6][7][8] Strong interfacial 9,10 and domain wall effects 11,12 also lead to a competing theory that charge separation is localized at the domain wall. 11,13 However, neither theory has convincing support of carrier and photo field dynamics with microscopic resolution.…”