Band edge versus deep luminescence of InxGa1-xN layers grown by molecular beam epitaxy

InxGa1-xN (0<x<0.2) thin layers were grown on GaN-coated sapphire substrates by molecular beam epitaxy (MBE) using ammonia as the nitrogen source. Their optical properties have been investigated by low- and room-temperature photoluminescence (PL) and photothermal deflection spectroscopy. It is shown that high-quality InxGa1-xN layers with x similar to 0.1 can be grown by MBE using NH3. The PL linewidths are 48 and 80 meV at 9 and 300 K, respectively. A bowing parameter of 1 eV is deduced for the band-edge luminescence energy. On the other hand, when the growth conditions slightly move aside the optimum, the PL spectra exhibit broad and deep luminescence. The variation of the PL energy of this deep luminescence as a function of the In composition is then discussed. (C) 1998 American Institute of Physics.