Electric field effects on excitons in gallium nitride

Electric field effects on Wannier excitons are observed for the first time in GaN thin films. Using both absorption and photocurrent measurements, we have studied the excitonic Franz-Keldysh effect in thin epitaxial GaN films at temperatures between 80 and 300 K. We have measured the Stark shift, quenching and broadening of the exciton peak with applied field. These results are compared with theoretical calculations from the literature. The physics of exciton ionization at varying temperatures is discussed which explains the interplay between absorption and photocurrent. An UV modulator based on the excitonic Franz-Keldysh effect is demonstrated.