Anomalous features in the optical properties of Al1-xInxN on GaN grown by metal organic vapor phase epitaxy

We have studied the optical properties of Al1-xInxN thin films grown on GaN by metal organic vapor phase epitaxy. X-ray diffraction analysis of omega and omega-2 theta scans showed that both the compositional fluctuation and the degree of crystalline mosaicity increase with increasing x. While the e nergy positions of both the absorption edge and photoluminescence peak shif t to a lower-energy region with increasing x, the linewidth of the photolum inescence spectra and the value of the absorption edge tail decrease. The S tokes shift also decreases with increasing x, following which both energy p ositions become 1.66 eV, which is smaller than the band gap of InN (1.9 eV) . These anomalous features of the optical properties of Al1-xInxN might be affected by the absorption in the infrared region caused by the high electr on concentration. (C) 2000 American Institute of Physics. [S0003-6951(00)02 507-9].