Observation of hot luminescence and slow inter-sub-band relaxation in Si-doped GaN/[Al.sub.x][Ga.sub.1-x]N (x=0.11, 0.25) multi-quantum-well structures

The growth, structural, electronic and optical properties of Si-doped GaN/[Al.sub.x][Ga.sub.1-x]N (x=0.11, 0.25) multiple-quantum-well structures grown on SiC by plasma-assisted molecular-beam epitaxy are reported. Inter-sub-band (ISB) relaxation times longer than 40 ps are measured in the GaN/AlGaN system, as a consequence of the quenching of the longitudinal optical (LO)-phonon emission when the ISB transition energy is below the LO-phonon energy.