Study of Exciton Dead Layers in GaN Schottky Diodes with N and Ga-Face Polarity

For the first time, we observed exciton dead layers in Pt/GaN Schottky diodes with N and Ga-face polarity. We show that these layers determine the shape of electroreflectance and photocurrent spectra close to the band gap in dependence on the bias voltage. Analysis of experimental data using a spatially dependent dielectric function of GaN due to an inhomogeneous electric field in the depletion region yields the ionised impurity concentration and the surface band bending. In addition, exciton and broadening energies for the field-free limit are obtained.