Undulation Spectra of GaP: N

Undulation spectra are observed in the luminescence of GaP: N codoped with an acceptor. New experimental data prove that the luminescence is a series of zero-phonon lines of excitons bound to N-acceptor pairs. The undulatory behavior originates from the averaged number of equivalent sites for different N-to-acceptor shells. Calculations show that this number has an approximately periodic fluctuation with the maxima separated by about 9 shells.