Coulomb-induced nonlinearities in GaN microdisks

Due to their wurzite structure, GaN quantum wells and dots arecharacterized by large built-in piezoelectric fields.These induce a spatial separation between the confined electron andholes, thus favouring the formation of electric dipoles.Here, we theoretically investigate the effects of the long-range,dipole-dipole interaction between two excitons in a GaN/Al(x)Ga(1-x)Nmicrodisk.These Coulomb interactions are shown to strongly affect the biexcitonground state. In particular, they induce strong spatial correlationsbetween the two excitons and result in biexciton binding energiesof the order of 1 meV.