Optical phonons in GaN/AlN quantum dots: leaky modes

Surface polar vibrations of a GaN quantum dot in AlN matrix are analyzed in the framework of the macroscopic dielectric continuum model. The conditions are found for existence of surface modes on a quantum dot of oblate spheroidal form. These conditions determine continuum frequency regions rather than quantized frequencies. The found modes are peculiar leaky states. They can provide effective energy relaxation of the confined electrons.