Relationship between residual carrier density and phase purity in InN grown by pressurized-reactor MOVPE

We have studied the relationship between the residual carrier density and the phase purity of the InN films grown on α-Al ₂O ₃ substrate by pressurized-reactor metalorganic vapour phase epitaxy. As simple and non-destructive measurement methods of carrier density (n _e), the plasmon dispersion analysis by the IR reflection spectra, and the estimation by the absorption edge of the IR transmission spectra have been adopted for the epitaxial InN films at room temperature, using Fourier transform infrared (FT-IR) spectrometer. With increasing the growth temperature, plasma frequency estimated from the reflectance analysis shifts to the lower frequency which means the decrease of n _e associated with the improvement of the crystal quality. Especially in case of zincblende containing InN grown at low temperature, the discrepancy occurred between n _e derived from two methods. The n _e analyzed in terms of the electronic band filling effect was found to be underestimated due to the use of bandgap energy of wurtzite phase instead of zincblende, since the bandgap energy of the latter has been reported to be 0.48 eV, much smaller than that of wurtzite, 0.68 eV.