Current transport and thermoelectric properties of very high power factor Fe3O4 / SiO2 / p-type Si (001) devices

TL;DR

This study investigates the electrical and thermoelectric behavior of Fe3O4/SiO2/p-type Si heterostructures, revealing high power factors and tunneling conduction mechanisms relevant for thermoelectric applications.

Contribution

It provides new insights into the conduction and thermoelectric properties of Fe3O4-based heterostructures, highlighting the role of interface tunneling and high Seebeck coefficients.

Findings

Sharp resistivity drop at 200K due to interface conduction

Seebeck coefficient reaches +1000 μV/K at 300K

Power factor of 70 mW/K^2m for 150 nm Fe3O4 layer

Abstract

The current transport and thermoelectric properties of Fe3O4 / SiO2 / p-type Si(001) heterostructures with Fe3O4 thicknesses of 150, 200, and 350 nm have been investigated between 100 and 300 K. We observe a sharp drop of the in-plane resistivity at 200K due to the onset of conduction along the Si / SiO2 interface related to tunneling of electrons from the Fe3O4 into the accumulation layer of holes at the Si / SiO2 interface, whose existence was confirmed by capacitance-voltage measurements and a two band analysis of the Hall effect. This is accompanied by a large increase of the Seebeck coefficient reaching +1000 {\mu}V/K at 300K that is related to holes in the p-type Si(001) and gives a power factor of 70 mW/K2m when the Fe3O4 layer thickness is reduced down to 150 nm. We show that most of the current flows in the Fe3O4 layer at 300 K, while the Fe3O4 / SiO2 / p-type Si(001) heterostructures behave like tunneling p-n junctions in the transverse direction.