Triple‐Site Dopant–Defect Complexes in Mg–H‐Codoped GaN: First‐Principles Identification

Abstract

There are dozens of double‐site and triple‐site dopant–defect complexes in Mg–H‐codoped GaN that can compensate the MgGa acceptor and thus limit p‐type conductivity; however, their properties have not been systematically studied. Using first‐principles calculations, herein, it is found that the well‐known double‐site complexes MgGa–VN and MgGa–HN can still act as donors, although they are already donor–acceptor‐compensated complexes. Therefore, they can compensate another MgGa acceptor and form the triple‐site complexes MgGa–MgGa–VN and MgGa–MgGa–HN, which have never been reported. The formation energies of the two triple‐site complexes can be low, especially in Ga‐rich and n‐type GaN, so they have non‐negligible concentration and thus play an important role in limiting the p‐type conductivity. The MgGa–MgGa–VN complex produces a defect level that can not only induce nonradiative electron–hole recombination, but also give rise to a red and broad photoluminescence band at 1.76 eV, providing another explanation for the red band observed in heavily Mg‐doped GaN. These triple‐site dopant–defect complexes should be taken into account in future study of defects in GaN and related semiconductors.