Influence of Heat on Impurity States in an Artificial Semiconductor Atom

The present work investigates the influence of heat on the donor
impurity states in a man-made artificial semiconductor atom (ASA) based on a
nano-meter scale, the so-called quantum dot (QD). An on-center donor
impurity is considered. The investigated nanostructure is composed of a GaAs
semiconductor as the potential well material of the ASA while an AlxGa1-xAs
semiconductor as the potential barrier material of the artificial atom. Different
heat dependent effective masses and different heat dependent dielectric
constants are used for the two semiconductors constitute the ASA. The lowest
energy and the binding energy of the ground state are calculated. The
calculations have shown that the lowest electron energy decreases by
increasing the ASA radius. For very large radii the lowest energies
corresponding to different aluminum contents approach a certain value which
is the bulk limit. At a constant ASA radius the lowest energy increases as a
function of temperature. A pronounced deviation is obtained when the
calculations of the present work are compared with those of Montenegro and
Merchancano [18] in which the effects of heat and mismatches for both
effective masses and dielectric constants were neglected. It is found that
decreasing the temperature and shrinking the radius of the ASA lead to more
binding of the donor electron. Increasing the aluminum concentration also
enhances the donor electron binding energy. Therefore the electron ground
state energy and its associated binding energy are both mainly functions of
temperature, ASA radius, and aluminum content.