Impact ionization of excitons in an electric field in GaN

The impact ionization of excitonic states is studied in epitaxial GaN films and GaN/AlGaN quantum well structures. The investigation is carried out by optical methods involving the observation of quenching of the exciton phot oluminescence under an applied electric field. It is found that impurity sc attering rules the momentum and energy relaxation, rather than the acoustic phonon scattering. The effective mean free path of hot electrons is estima ted. In GaN/AlGaN quantum wells the mean free paths of hot electrons appear to be an order of magnitude larger than those of GaN films due to the decr ease in scattering probability of the electron in the two-dimensional case.