Intersubband population inversion under resonance tunnelling in wide quantum well structures

The possibility of intersubband population inversion and the necessary conditions for its achievement in wide quantum well structures with the energy space between the lowest states being lower than the optical phonon energy are considered. Two possible designs are proposed, both using resonant tunnelling for selective depopulation of the lowest subband. The analysis of resonance tunnelling times and intersubband relaxation rates due to various scattering processes is carried out, demonstrating the possibility, at sufficiently low carrier concentrations, of inverted carrier distributions over the lowest subbands under optical pumping or electrical injecting conditions.