High-mobility SrTiO$_3$ delta-doped field-effect transistors

Two-dimensional electron systems in SrTiO$_3$ show intriguing properties such as high mobility transport, magnetism, and possible unconventional superconductivity. A delta-doped structure, sandwiching a narrow two-dimensional conducting SrTiO$_3$ channel between two insulating SrTiO$_3$ layers, provides a clean platform to realize such electronic states, with symmetric confining potential in the absence of interface or surface scattering. Electric field gating of the conducting channel in a field-effect transistor (FET) geometry is a powerful method for tuning low-dimensional systems via carrier density modulation. We have synthesized high quality SrTiO$_3$ delta-doped structures using pulsed laser deposition, and optimized the device processing steps to achieve ideal FET characteristics at room temperature. This progress enabled examination of high-mobility transport in the carrier density regime as low as 3 $\times$ 10$^{12}$ cm$^{-2}$ at low-temperatures, opening promising avenues to investigate quantum transport and realization of exotic quantum phases in SrTiO$_3$ two-dimensional electron systems.