Intervalley Relaxation Processes of Shallow Donor States in Germanium

The role of intervalley processes in electron–phonon interaction for the relaxation of excited shallow arsenic donors in germanium is analyzed. The rates of intracenter intervalley transitions with the emission of TA phonons in germanium are calculated depending on the uniaxial compression stress along the {111} crystallographic direction. It is shown that the intervalley transitions to the donor ground state with the emission of phonons can play a significant role in the relaxation of excited impurities only upon uniaxial stress of the crystal, since there are no exact resonances between the impurity transitions and intervalley phonons at zero stress. There are also transitions from highly excited states lying in a narrow band of energies (~0.5 meV) near the very bottom of the conduction band to the first excited state 1 s (3) (Γ 5 ) (in stressed Ge to 1 s (3) (Γ 3 ). The average rate of these transitions is estimated as 0.3 × 10 9 s –1 .