Electrical properties and optical bandgaps of AlInN films by reactive sputtering

c-Axis-oriented AlxIn1−xN (AlInN) films (0.12⩽x⩽0.87) were grown on AlN/glass substrates by pulsed-dc reactive sputtering. The deposited AlInN films have excellent crystal quality without oxygen contamination. The electron concentrations of sputtered In-rich films are lower than 3×1018 cm−3 for x⩾0.36. The composition dependence of the bandgap is discussed and compared with previous reports. The bandgap discrepancy of In-rich films grown by different methods can be explained by Burstein–Moss effect. The bowing parameter for bandgaps of AlInN films is calculated as 4.1 eV by polynomial fitting. The extrapolated bandgap from bowing equation is 6.0 eV for AlN.