Contribution of free-electron recombination to the luminescence spectra of thick GaN films grown by hydride vapor phase epitaxy

Hydride vapor epitaxy grown thick unintentionally doped GaN film on sapphire is investigated. In the near bandgap regions of the photoluminescence and cathodoluminescence spectrogram, a broad asymmetric band extending to energies above the band gap is observed in addition to sharp exciton emission lines. This phenomenon is analyzed as a free-electron recombination band. The spectra of lightly doped regions which contain only sharp bound exciton, the spectra of highly doped regions which show both thee broadband only, and the spectra of the areas containing surface defects which show both spectral simultaneously are analyzed using spatially resolved cathodoluminescence.