Yellow luminescence and related deep levels in unintentionally doped GaN films

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Abstract
The deep level energy distribution associated with the well-known “yellow luminescence” in GaN is studied by means of two complementary deep level techniques: photoluminescence and surface photovoltage spectroscopy. The combined experimental results show that the yellow luminescence is due to capture of conduction band electrons, or electrons from shallow donors (with a maximum depth on the order of the thermal energy) by a deep acceptor level with a broad energy distribution, centered at ∼2.2 eV below the conduction band edge. In addition, the results show that the density of yellow luminescence related states possesses a significant surface component.