Three-Electrode Device for Applying Two-Dimensional Vector Electric Fields to Single In As Quantum Dots

Electric field tuning of single $\mathrm{In}\mathrm{As}$ quantum dots (QDs) provides an important tool for physics experiments and for the development of scalable and in situ--tunable devices. Control of a single QD with either a growth direction or an in-plane electric field is well established, but a device that can apply the two-dimensional (2D) vector electric fields necessary to simultaneously and independently tune more than one parameter has not yet been demonstrated. We use comsol multiphysics simulations to illustrate the device-design challenges in applying a uniform 2D electric field in a $\mathrm{Ga}\mathrm{As}$ solid-state system and to systematically explore the effects of electrode coverage, mesa size, and doping on the device performance. We develop and present a design that can apply 2D electric fields to a single QD while remaining compatible with optical experiments. We then fabricate and characterize a proof-of-concept device that validates the design presented here. We discuss the applications for this device and the potential for full 2D-electric-field control of a single QD or a quantum-dot molecule.