  In developing our previous contribution (arXiv:1804.00889) we have
numerically found the bound state energy and correspondent wave function of the
two electrons confined to move in a quantum well placed close to the gate
electrode. Spin-orbit interaction (SOI) and image charge forces result in
effective attraction between electrons. We considered also the effect of gate
voltage applied to the structure and discovered that this can essentially
increase the bound energy of the pair so that it remains stable even at room
temperature.
