Electronic and Shallow Impurity States in Semiconductor Heterostructures Under an Applied Electric Field**The projectsupported by the Natural Science Foundation of Shanghai Municipal Commission ofEducation under Grant No. 99QF55

Abstract

With the use of variational method to solve the effective mass equation, wehave studied the electronic and shallow impurity states in semiconductorheterostructures under an applied electric field. The electron energy levelsare calculated exactly and the impurity binding energies are calculated withthe variational approach. It is found that the behaviors of electronic andshallow impurity states in heterostructures under an applied electric fieldare analogous to that of quantum wells. Our results show that with theincreasing strength of electric field, the electron confinement energiesincrease, and the impurity binding energy increases also when the impurityis on the surface, while the impurity binding energy increases at first, toa peak value, then decreases to a value which is related to the impurityposition when the impurity is away from the surface. In the absence ofelectric field, the result tends to the Levine's ground state energy(-1/4 effective Rydberg) when the impurity is on the surface, and the groundimpurity binding energy tends to that in the bulk when the impurity is faraway from the surface. The dependence of the impurity binding energy on theimpurity position for different electric fieldis also discussed.