A NOVEL SECULAR EQUATION FOR THE COUPLED-BAND ENVELOPE-FUNCTION APPROXIMATION FOR SUPERLATTICES AND APPLICATION TO INAS INXGA1-XSB SUPERLATTICES/

This paper derives and demonstrates a new secular equation for the cou pled-band envelope-function approximation (EFA) formalism for superlat tices in order to overcome the difficulty of handling rapidly growing or decaying wavefunction components, in particular, the 'wing solution s'. In a second development, the generally nonHermitian secular equati on is made Hermitian, making it easier to locate multiply degenerate r oots. In the process, the simple Kronig-Penney model is recast into a form closely related to that for the underlying quantum well (QW) prob lem. The present method is applicable to Burt's EFA formalism. An InAs /InGaSb type-II superlattice is used to demonstrate the method. (C) 19 97 Academic Press Limited.