Characterization of low Al content AlxGa1−xN epitaxial films grown by atmospheric-pressure MOVPE



AlxGa1−xN epitaxial films grown on GaN/sapphire by atmospheric-pressure metalorganic vapor phase epitaxy (AP-MOVPE) using trimethylgallium (TMG) and trimethylaluminum (TMA) as group III precursors have been studied. Two groups of samples were grown. The aluminum (Al) solid composition of AlxGa1−xN was varied in the range from 0.03 to 0.20 by changing the molar flow ratio [TMA/(TMA + TMG)]. The effect of TMA flow rate, respectively, TMG flow rate, on the growth rate, and Al solid composition is discussed. The structural properties of the alloys have been investigated by high-resolution X-ray diffraction (HRXRD). The optical properties of these samples were investigated by photoluminescence (PL). It is found that on increasing Al solid composition, via an increase of the TMA flow rate, the structural quality is deteriorated and the growth efficiency decreases. On the other hand, when the TMG flow rate is reduced, a decrease of the full width at half-maximum (FWHM) is observed with Al content.