  The confinement mechanism of electrons in gated circular quantum dots is
studied in a sequence of models, from self-consistent 3D Hartree calculations
to the semiclassical model of Shikin et al. Separation of the vertical from
transverse confinement allows accurate 2D Hartree calculations. For moderate
size dots containing $\sim 50$ electrons, 2D Thomas-Fermi can also be accurate.
Finally, a Shikin type parameterization of the electron density allows
quantitative study of the importance of the many contributions to the
confinement potential.
