Enhanced luminescence from AlxGa._xN/AlyGa ._yN quantum wells grown by gas source molecular beam epitaxy with ammonia

We report the structural and optical properties of AlxGaJ.xN/AlyGal_yN quantum wells (QWs) structures grown by gas source molecular beam epitaxy with ammonia on sapphire (0001) substrates. QWs structures consist of five pairs of AlyGal_yN, O.3<y<0.45, wells (nominally 2-4 nm thick) and AlxGa]_xN, O.55<x<1, barriers (nominally 5 nm thick). All the structures were completed with a 10 run thick cap layer of AIN. We observed a significant enhancement in the cathodoluminescence intensities and longer photoluminescence lifetimes for OW structures grown in the 3D mode, as confirmed by spotty reflection high energy electron diffraction patterns. These effects are attributed to the formation of AlGaN quantum dots in the well materials.