Trapping of electrons into neutral impurities in semiconductors in a quantizing magnetic field

We consider the trapping of electrons into shallow neutral donors with a sh ort-range potential (r(c) much less than l(H), where l(H) = root c (h) over bar/eH is the magnetic length) due to the emission of an acoustic phonon i n a semiconductor in the presence of a quantizing magnetic field (T much le ss than (h) over bar omega(H), where omega(H) is the cyclotron frequency an d T is the temperature). It is demonstrated that, when carriers are charact erized by an isotropic effective mass and the impurity-compensation degree is sufficiently low, trapping into shallow neutral impurities may dominate over trapping into ionized Coulomb centers. The dependence of the coefficie nt of carrier trapping on the carrier energy is shown to change as the carr ier energy approaches the bottom of some Landau band: the inverse lifetime becomes proportional to the transmission coefficient of a particle through a one-dimensional effective impurity potential averaged over the transverse motion of an electron in the magnetic field. Trapping into small-radius ne utral impurities is investigated in the case of a sharply anisotropic mass of carriers. It is demonstrated that, in this case, the carrier lifetime wi th respect to trapping into magnetic-impurity states of an impurity with a short-range potential oscillates as a function of the magnetic field. The r evealed oscillations are periodic in the magnetic field as H-1/4. Th, possi bility of the experimental observation of carrier trapping into neutral imp urities in fourth-group semiconductors in a quantizing magnetic field with the use of infrared (FIR) lasers is discussed.