Large Electron Concentration Modulation using Capacitance Enhancement in SrTiO3/SmTiO3 FinFETs

TL;DR

This study demonstrates that fin structure design in SrTiO3/SmTiO3 FETs significantly enhances gate capacitance, enabling record 2DEG electron concentration modulation in complex oxide heterostructures.

Contribution

The paper introduces a method of geometrical capacitance enhancement in SrTiO3/SmTiO3 FinFETs, achieving unprecedented electron density modulation.

Findings

FinFETs show higher gate capacitance than planar FETs.

Scaling fin widths further increases capacitance.

Record electron concentration modulation of ~2.4 x 10^14 cm^-2 achieved.

Abstract

Solid-state modulation of 2-dimensional electron gases (2DEGs) with extreme (~3.3 x 1014 cm-2) densities corresponding to 1/2 electron per interface unit cell at complex oxide heterointerfaces (such as SrTiO3/GdTiO3 or SrTiO3/SmTiO3) is challenging because it requires enormous gate capacitances. One way to achieve large gate capacitances is by geometrical capacitance enhancement in fin structures. In this work, we fabricate both Au-gated planar field effect transistors (FETs) and Fin-FETs with varying fin-widths on 60nm SrTiO3/5nm SmTiO3 thin films grown by hybrid molecular beam epitaxy (hMBE). We find that the FinFETs exhibit higher gate capacitance compared to planar FETs. By scaling down the SrTiO3/SmTiO3 fin widths, we demonstrate further gate capacitance enhancement, almost twice compared to the planar FETs. In the FinFETs with narrowest fin-widths, we demonstrate a record 2DEG electron concentration modulation of ~2.4 x 1014 cm-2.