CONDUCTION SUBBANDS IN A GAAS/ALXGA1-XAS QUANTUM-WELL - COMPARING DIFFERENT K.P MODELS

The energy dispersion of the conduction subbands in a GaAs/AlxGa1-xAs superlattice is calculated by using a k.p Hamiltonian that includes different number of bands. The most accurate model includes the GAMMA6c, GAMMA7v, GAMMA8v, GAMMA7c, and GAMMA8c bands. The resulting subband dispersion is compared with that obtained when the coupling of the GAMMA6c band with the GAMMA7v and GAMMA8v and/or GAMMA7c and GAMMA8c bands is neglected. We also consider the 2X2 k-p Hamiltonian with terms up to the order k4. The subband dispersions are analyzed quantitatively by fitting the numerical result to the analytical expression obtained with the invariant expansion technique. The subbands are found to be significantly different with the various models. The differences are ascribed to the different bulk band dispersions obtained with different k.p Hamiltonians and to the variation of the band parameters in the well and barrier materials.