Thermodynamics of quasi-2D electron gas at BFO/Si interface probed with THz time-domain spectroscopy

An interface is constructed based on a bismuth ferrite oxide (BFO) thin film and p-type silicon, and the temperature dependence of the interface properties has been studied systematically using terahertz time-domain spectroscopy. The BFO/Si interface exhibits quasi-two-dimension electron gas (2DEG) transport in the temperature range of 80 to 140 K: the electrons at the interface possess large electron mobility (∼10 6 cm 2 /V s) and long scattering time (∼100 ps). As the temperature is higher than 140 K, an abrupt decrease in THz interface conductivity is observed due to the breakdown of the 2D EG induced by the surface phase transition in the BFO thin film. Our result reveals that the interface formed between BFO and Si provides a special platform for designing and fabricating THz photonic devices.