Quantum cascade laser design based on impurity-band transitions of donors in Si/GeSi(111) heterostructures

摘要

The possibility of amplification of terahertz radiation due to optical transitions between a two-dimensional state continuum (2D) and shallow-level donor states in Si/GeSi(111) superlattices with selectively 8-doped quantum wells is analyzed theoretically. The mechanism of population inversion is based on fast ionization of donor centers by phonon-assisted tunneling into continuum of a lower subband in the neighboring quantum well. The fast tunneling is caused by hybridization of the impurity ground state and a 2D state continuum in the neighboring quantum well. It is shown that for the donor concentration of 5 × 10~(11) cm~(-2) per period the terahertz gain can be as high as 10 cm~(-1) in the wavelength range of 29-45 μm (6.5-10.2 THz).