Positive impurity size effect in degenerate Sn-doped GaN prepared by pulsed sputtering

This study reports on the epitaxial growth of heavily Sn-doped GaN films by pulsed sputtering deposition (PSD) and their basic characteristics, which include electrical, optical, and structural properties. Heavily Sn-doped GaN yielded a maximum electron concentration of 2.0 × 1020 cm−3 while keeping an atomically flat surface. The high electron concentration was confirmed by Raman spectroscopy measurements. X-ray diffraction analysis revealed that the Sn dopants exhibited a positive-size effect coefficient, which is opposite to conventional n-type dopants, such as Si and Ge. Furthermore, the shifts toward higher energy of optical bandgap energies and near-band edge emission peaks clearly indicated the highly degenerated nature of the PSD-grown Sn-doped GaN. These results indicate that the introduction of Sn atoms is quite promising for stress control in n-type GaN.