Extreme charge density SrTiO3/GdTiO3 heterostructure field effect transistors

We report on the fabrication and electrical characteristics of the first SrTiO3/GdTiO3 (STO/GTO) heterostructure field-effect transistors (HFETs). The high two-dimensional electron gas (2DEG) density of 3 × 1014 cm−2 formed due to the polar discontinuity at the STO/GTO interface was used as a channel to create inverted HFETs. Plasma O2 treatment was found to reduce current leakage by 3 orders of magnitude at reverse bias, leading to rectifying Schottky behavior. A charge modulation of 0.6 × 1014 cm−2 is reported here, which represents the highest sheet charge modulated in any planar field effect transistor to date.