Drag current for ionization of impurities by an electromagnetic wave in a semiconductor superlattice

The drag current for ionization of a shallow impurity by a strong electromagnetic wave in a semiconductor superlattice is found. It is shown that at low temperatures, when it is possible to ignore the equilibrium carrier density, the dependence of the drag current on the intensity of the electromagnetic wave is nonlinear and it oscillates with growth of the intensity of the electromagnetic field. These oscillations are a consequence of the many-photon character of absorption of the electromagnetic wave by the impurities and also of nonparabolicity of the energy spectrum of the superlattice. A comparison is made of the contributions to the drag current from the anisotropic part of the impurity ionization probability and from its isotropic part, with allowance for modification of the distribution function by the electromagnetic wave. It is found that for (ℎ/2π)ω<<Δ (Δ is the width of the conduction miniband) the main contribution to the drag current comes from the isotropic part of the ionization probability