ANISOTROPIC POLARONS NEAR INTERFACES OF POLAR SEMICONDUCTORS

The interactions of a slow electron with the interface and bulk modes of two semi-infinite polar semiconductors are discussed with the anisotropic mass of the electron taken into account. We obtain an expression for the effective interaction between the electron and these modes which reduces to the expression obtained from image-potential theory if the electron is far from the interface. When the electron is near the interface, the effective potential differs from the image potential and becomes nonlocal. We have used a generalization of the Lee-Low-Pines method to calculate the binding energy and the electron-mass renormalization due to the coupling of the electron and the interface modes and bulk LO phonons. This theory is applied to the heterojunction AlAs and GaAs, when the electron is at the X high-symmetry point of the conduction band of AlAs. We also study the effects of an external static electric field applied perpendicular to the interface and calculate the binding energy and the effective-mass correction parallel to the interface as a function of the electric field intensity. © 1990 The American Physical Society.