Valence subband structures and optical properties of strain-compensated quantum wells

The strain compensation effects on the valence subbands and on the optical properties of CaInAs/AlCaInAs quantum well structures are theoretically studied for the first time. In the case of compressive-strained quantum wells, where the top valence subbands are always formed with heavy hole (HH) subbands, the compensatingly tensile-strained barriers shift the first light hole (LH) subbands upward increasing the valence band mixing between them, and significantly reducing the transverse electric (TE) gain. In contrast, in the tensile-strained quantum wells whose top valence subband is formed with LH subband, the compensatingly compressive-strained barriers shift the top LH subband downward and on some occasions the top LH subband is replaced with the first HH one. The increase of the TE gain is relatively small due to the strong valence band mixing. The strain of the barrier layers is found to play an important role in the valence subband structures and optical properties.