Proposed explanation of the anomalous doping characteristics of III-V nitrides

Anomalous doping characteristics of III-V nitrides are explained on the basis df experimental methods. To our knowledge, this is the first successful experimental attempt to address the doping difficulties with the p- and n-type III-V nitrides. GaN is used as the test system. Our results strongly suggest that N vacancies (V-N), creating donor-like states at or very near the conduction-band edge, are responsible for natural n-type doping characteristics of undoped samples. The samples cannot be doped p type even by introducing a large content of p-type dopant atoms, unless the natural n-type character is nullified by minimizing the presence of V-N. This can be done by increasing the ammonia flow rate significantly during epitaxial growth. However, excessive flow of ammonia leads to the generation of donor-like N antisites. Compensation of holes of the acceptor states by electrons of these donor-like states, and the high binding energy of the acceptor atoms hinder the realization of high p-type doping.