Improved laser performance due to spatial separation of heavy- and light-hole states in compressive- and tensile-strained structures

We show that the degree of overlap between the envelope functions of heavyand light-hole states can affect the in-plane dispersion of the highest hole subband. We consider ways to reduce this overlap by spatially separating the heavy- and light-hole states to different layers, while maximizing their energy separation. Strain-compensated superlattice structures where opposite strains are introduced in the well and barrier regions offer such possibilities and lead to a significant increase of the optical gain and a reduction of the threshold current density in semiconductor lasers. Well materials under biaxial compression for transverse electric (TE) emission or under tension for transverse magnetic (TM) emission are considered using the InGaAsP system grown on InP for the former and the AlGaAsSb system grown on GaSb for the latter.