Phonon-Assisted exciton tunneling in GaAs sub x P sub (1-x):N.

The low temperature photoluminescence of GaAs sub x P sub (1-x):N(x <= 0.7) crystals has been studied under selective excitation into the nitrogen related exciton band (N sub X). The spectra consists of several features whose relative intensity depends on the excitation energy. Excitons created on non- transferring (terminal) states give rise to a sharp line, (B'), 0.9 meV below the exciting laser line. Excitons in transferring states tunnel to lower energy states by acoustic phonon assisted processes. This results in broad phonon sidebands. We introduce a model for exciton transfer and fit both the band shapes and their relative intensity. We thus find that the most probable tunneling process involves single phonon emission and that the dominant interaction mechanism between excitons and zone- center acoustic phonons is the deformation potential.