Sources of carrier compensation in n-type and p-type GaN layers grown by metalorganic vapor phase epitaxy were quantitatively identified by a combination of Hall-effect analysis and deep level transient spectroscopy. For n-type GaN, we identified three electron compensation sources: residual carbon atoms likely sitting on nitrogen sites (CN), an electron trap at the energy level of EC –0.6 eV (the E3 trap), and self-compensation appearing with increasing donor concentration. We showed that the CN also play a key role in hole compensation in p-type GaN by forming donor-like charged states. We also investigated the reduction of acceptor concentrations (Na) in highly Mg-doped GaN. Atomic-resolution scanning transmission electron microscopy revealed that electrically inactive Mg atoms of 3/2 atomic layers are segregated at the boundary of pyramidal inversion domains. The Na reduction can be explained by this Mg segregation.

The source of carrier compensation in metalorganic vapor phase epitaxy (MOVPE)-grown n-type GaN was quantitatively investigated by Hall-effect measurement, deep-level transient spectroscopy, and secondary ion mass spectrometry. These analysis techniques revealed that there were at least three different compensation sources. The carrier compensation for samples with donor concentrations below 5 × 1016 cm−3 can be explained by residual carbon and electron trap E3 (EC − 0.6 eV). For samples with higher donor concentrations, we found a proportional relationship between donor concentration and compensating acceptor concentration, which resulted from a third source of compensation. This is possibly due to the self-compensation effect.