Practical Application

In this section, the practical utility of QTCAD is demonstrated through its application to model a realistic gated quantum dot. In the first part of this section, we use devicegen to construct a mesh for our entire device (including gate structure and heterostructure stack) based on a photomask layout for the gate structure of the dot. In the second part, we solve the nonlinear Poisson equation throughout the entire device to obtain the quantum dot’s confinement potential and then solve the Schrödinger equation in the dot to obtain the eigenenergies and eigenfunctions of electrons confined within the dot. In the third part, we repeat calculations similar to those of the previous part, except that the confinement potential in the quantum dot is obtained via the quantum-well solver, which models quantum confinement along the heterostructure growth direction. In the fourth part, we repeat the calculations of the second part over a wider range of plunger gate voltages—this enables us to examine the dependence of the dot’s ground-state energy on the gate voltage and thereby extract the lever arm. In the fifth part, we investigate transport through the dot in the Coulomb blockade regime—specifically, we compute the Coulomb peaks. In the sixth part, we further examine transport through the dot over a range of drain–source voltages—this leads us to obtain the charge-stability diagram of the dot. In the seventh part, we consider a voltage configuration where only one electron resides in the dot. We then drive oscillations between the two lowest-energy states of the dot (i.e. Rabi oscillations) through electric dipole spin resonance. Finally, in the eighth part, we model the effect of charge noise on such Rabi oscillations.