The relaxation times of donor bound electrons in germanium

The results of investigations of relaxation processes of donor bound electrons in the germanium doped by arsenic at cryogenic temperatures are presented. The lifetimes of p-type excited states of a donor were measured by pump-probe technique utilizing THz radiation from free-electron laser NovoFEL. The uniaxial stress along [111] axis was applied to the crystal to modify the energy spectrum of the impurity and intervalley relaxation processes. The analysis of experimental for p-type excited states allows to get the upper limit for the relaxation time of lowest 1s excited state. The comparison of obtained experimental results with the theoretical estimates for the interaction with TA phonons indicates on the enhancement of the interaction with the phonons having wavenumbers corresponding to the flat part of the dispersion.