Overview of carrier compensation in GaN layers grown by MOVPE: toward the application of vertical power devices

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 (C N ), an electron trap at the energy level of E C –0.6 eV (the E3 trap), and self-compensation appearing with increasing donor concentration. We showed that the C N 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 ( N a ) 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 N a reduction can be explained by this Mg segregation.