Influence of Heat on Impurity States in an Artificial Semiconductor Atom

Abstract

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 Al x Ga 1-x As 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.