Band gap bowing parameter in pseudomorphic AlxGa1-xN/GaN high electron mobility transistor structures

A method for evaluation of aluminium composition in pseudomorphic AlxGa1-xN layer from the measured photoluminescence (PL) peak energy is presented here. The layers were grown by metalorganic chemical vapor deposition and characterized by high resolution X-ray diffraction (HRXRD), PL, cathodoluminescence, and atomic force microscopy. We estimated the value of biaxial stress in pseudomorphic AlxGa1-xN layers grown on sapphire and silicon carbide substrates using HRXRD scans. The effect of biaxial stress on the room temperature band edge luminescence in pseudomorphic AlxGa1-xN/GaN layers for various aluminium compositions in the range of 0.2 < x < 0.3 was determined. The value of pressure coefficient of band gap was also estimated. The stress corrected bowing parameter in AlxGa1-xN was determined as 0.5060.06 eV. Our values match well with the theoretically obtained value of bowing parameter from the density functional theory. (C) 2015 AIP Publishing LLC.