Improvement on epitaxial grown of InN by migration enhanced epitaxy

Epitaxial growth of InN on (0001) sapphire with an AlN buffer layer was studied by migration-enhanced epitaxy, which is composed of an alternative supply of pure In atoms and ${\mathrm{N}}_{\mathrm{2}}$ plasma. A series of samples were prepared with different substrate temperatures ranging from 360 to 590 °C. As-grown films were characterized by x-ray diffraction (XRD), reflective high-energy electron diffraction, atomic-force microscopy (AFM), and Hall measurements. Both XRD θ–2θ and ω scans show that the full width at half maximum of the (0002) peak nearly continuously decrease with increasing growth temperature, while InN grown at $\text{590\hspace{0.05em}°}\mathrm{C}$ shows the poorest surface morphology from AFM. It is suggested that three-dimensional characterization is necessary for an accurate evaluation of the quality of the InN epilayer. Hall mobility as high as $\text{542\hspace{0.5em}}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V s}$ was achieved on film grown at $\text{∼500\hspace{0.05em}°}\mathrm{C}$ with an electron concentration of ${\text{3×10}}^{18}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}}$ at room temperature. These results argue against the common view that nitrogen vacancies are responsible for the high background n-type conductivity of InN. To illuminate the relationship between Hall mobility and carrier concentration, the electrical properties of all InN films grown recently were summarized.