Effect of C-doping on near-band gap luminescence in bulk GaN substrates grown by halide vapor phase epitaxy

• Freestanding bulk C-doped GaN substrates grown by halide vapor phase epitaxy were studied by optical spectroscopy and electron microscopy. In cathodoluminescence (CL) the yellow line (YL) was more intense in samples with higher C content and stable in the temperature range 5-300 K. CL mapping in situ a scanning electron microscope revealed pitlike structure of the layers with higher YL intensity in the pits related to higher local oxygen incorporation. Near bandgap (NBG) emission studies of the pits revealed donor-bound excitons (DBE) with broad emission and no significant acceptor bound exciton (ABE) emission. Pit-free areas demonstrate two well-resolved ABEs with DBE quenched. Quenching of the DBE is explained by potential fluctuations in the vicinity of the carbon atoms in the pits-free regions lowering the ionization barrier for DBE.

Nyckelord

Bulk GaN

carbon doping

luminescence

bound excitons

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