RF-Molecular Beam Epitaxy Growth and Properties of InN and Related Alloys

The fundamental band gap of InN has been thought to be about 1.9 eV for a long time. Recent developments of metalorganic vapor phase epitaxy (MOVPE) and RF-molecular beam epitaxy (RF-MBE) growth technologies have made it possible to obtain high-quality InN films. A lot of experimental results have been presented very recently, suggesting that the true band-gap energy of InN should be less than 1.0 eV. In this paper, we review the results of the detailed study of RF-MBE growth conditions for obtaining high-quality InN films. The full widths at half maximum (FWHMs) of ω-mode X-ray diffraction (XRD), ω–2θ mode XRD and E₂ (high-frequency)-phonon-mode peaks in the Raman scattering spectrum of the grown layer were 236.7 arcsec, 28.9 arcsec and 3.7 cm^-1, respectively. The carrier concentration and room temperature electron mobility were 4.9×10¹⁸ cm^-3 and 1130 cm²/Vs, respectively. Photoluminescence and optical absorption measurements of these high-quality InN films have clearly demonstrated that the fundamental band gap of InN is about 0.8 eV. Studies on the growth and characterization of InGaN alloys over the entire alloy composition further supported that the fundamental band gap of InN is about 0.8 eV.