On the Intracenter Relaxation of Shallow Arsenic Donors in Stressed Germanium. Population Inversion under Optical Excitation

Abstract

The relaxation rates of lower excited states 1s(T), 2p₀, 2s, 3p₀, and 2p_± of arsenic donors in a germanium crystal are calculated upon the interaction with long-wavelength acoustic phonons depending on the uniaxial stress in the crystallographic direction [111]. The populations of states under optical excitation are estimated for calculated times. It is shown theoretically that optical excitation of the medium forms an inverse population of arsenic donor levels and leads to the possibility of the implementation of a four-level laser scheme with the radiative transition between 2p states and the 1s triplet state at zero strain. The estimated value of the expected gain in the medium under optical excitation conditions by CO₂ laser radiation in the medium at a donor concentration of 2 × 10¹⁵ cm^–3 is ~0.35 cm^–1 at a frequency of 1.98 THz if the laser transition is 2p_± → 1s(T) and 1.25 THz if the laser transition is 2p₀ → 1s(T).