The Effect of Nanostructure on Near-Infrared Absorption in M-Plane AlGaN/(In)GaN Heterostructures*

Near infrared intersubband (ISB) absorption of nonpolar Al_xGa_1-xN/(In)GaN is studied due to its broad potential applications into optoelectronic devices. Above 60% Al-composition, m-plane AlGaN alloy becomes kinetically unstable during the plasma-assisted molecular beam epitaxy growth generating unique nanostructures. The nanostructures are imaged with energy dispersive x-ray spectroscopy and scanning transmission electron microscopy. They consist of platforms of higher than expected Al-composition and islands of lower Al-composition AlGaN. We discuss the consequences of these nanostructures on ISB absorption energy and linewidth. We are also investigating strain-balanced Al_xGa_1-xN/InGaN (x<0.6) as an alternative to Al_xGa_1-xN/GaN (x>0.6).