The type-I nanoscale heterostructure Al0.3Ga0.7As0.03Sb0.97/ GaAs0.6Sb0.4/ Al0.3Ga0.7As0.03Sb0.97 grown on GaSb substrate at room temperature (300K) has been investigated in this paper. The injected carrier concentration has been set at 2.5 x 1012/cm2. The design is modelled with k.p technique using 4x4 Luttinger-Kohn Hamiltonian model with conduction band. The effects due to external temperature and strain have also been investigated. The energy wavefunctions, dispersion profile, optical gain etc have been computed for lasing wavelengths in mid infrared region.