Si doping at GaN inversion domain boundaries: an interfacial polar field for electron and hole separation

Using first-principles calculations, we investigated the phenomenon of Si doping at the GaN inversion domain boundaries (IDB) perpendicular to the wurtzite [0001] axis. The results reveal that the half monolayer Si doped GaN IDB is more stable than the abrupt monolayer Si doped IDB. This finding is vital to understanding the unique growth mechanism of Si-induced IDBs in N-polar GaN nanowires that are embedded in a Ga-polar layer [Nano Lett., 2012, 12, 6119]. The lower-energy boundary exhibits the characteristics of intrinsic semiconductor and fulfils the electron counting rule. Charge neutrality is achieved by transferring electrons from the Si–N to the Ga–Ga bonds. Moreover, a potential step is induced by the asymmetric substitution of Si for Ga atoms at the interface, which facilitates the spatial separation of excited carriers at this neutral boundary. Our results suggest an alternative strategy for designing novel and highly efficient photovoltaic devices.