Question

How electrons confinement tke place between by palacing a direct band gap material between two larger band gap material hence increasing the poplation inversion

Answer 1

if one see the band structure (energy -wave vector diagram) of the  semiconductor  and if  maximum of valence band and minimum of conduction band lie exactly in vertical position (maybe on vertical axis) then that semiconductor would have direct band gap otherwise semiconductor has indirect band gap. it actually relates to photon-phonon coupling in transition probability of electron jumping from valence band to conduction band