SURFACE GREEN-FUNCTION MATCHING FOR SYMMETRICAL STRUCTURES - OPTICAL PHONONS IN A DOUBLE-BARRIER STRUCTURE

A surface Green function matching (SGFM) analysis is formally develope d for planar multilayer structures having mirror image symmetry so tha t (i) matching is effected at only one half of the interfaces and (ii) even and odd solutions are obtained separately from different factori sed SGFM problems for each parity. This may be very useful in avoiding problems of numerical resolution when eigenvalues of opposite parity are closely spaced. The practical usefulness of the factorised SGFM me thod is demonstrated by applying it to the study of long wave polar op tical phonons in a GaAs-based A-B-A-B-A double barrier resonant tunnel ling structure and this is compared with the corresponding simple quan tum well B-A-B in which the B barriers are semi-infinite. The results show some interesting features and indicate that, depending on design parameters, the long range electrostatic coupling across even fairly t hick barriers may have strong effects on the electrical spectral stren gth of the modes, which should affect significantly the electron-phono n interaction.