Correlations between electrical and optical properties for OMVPE InN

Abstract

An experimental study has been made of correlations between electrical and optical properties for OMVPE InN grown on sapphire substrate. Carrier concentration for a grown film is found to decrease with increasing growth temperature and shows the lowest value 5.8×10 18 cm −3 at 600°C. A strong photoluminescence (PL) with a peak energy of 0.7–0.8 eV is observed at room temperature. As a general trend, PL peak energy and optical absorption edge increase with increasing carrier concentration (Burstein–Moss shift). For relatively thick films with large grains, grown at a relatively high temperature, a discrepancy is found between carrier concentration obtained by Hall measurement and PL data. Such samples show a PL spectrum with a lower peak energy and a smaller FWHM in spite of a higher carrier concentration. Although Hall measurement gives a carrier concentration as high as 2.3×10 19 cm −3 for the sample grown at 620°C, this sample should have a much lower carrier concentration because the PL peak energy is lower than that for the sample with the lowest carrier concentration 5.8×10 18 cm −3. These results show that the optimum growth temperature is higher than 600°C determined from the electrical characterisation.