Spatio-time-resolved cathodoluminescence study on high AlN mole fraction AlxGa1−xN structures grown by metalorganic vapor phase epitaxy

摘要

Concept, equipment, and exploitation of spatio-time-resolved cathodoluminescence (STRCL) spectroscopy will be presented. As one of its advantages is unlimited bandgap energy of the sample, we show STRCL data of high AlN mole fraction AlxGa1-xN structures. For understanding the mechanisms of the improvement in the luminescence efficiency of Al0.68Ga0.32N/Al0.77Ga0.23N multiple quantum wells by proper Si-doping in the wells, STRCL measurements and self-consistent Schrödinger-Poisson calculations were carried out, and positron annihilation measurement was carried out on Al0.6Ga0.4N films with various Si-doping concentrations. The increase in the luminescence lifetime at room temperature, which reflects the decrease in the concentration of nonradiative recombination centers (NRCs), is correlated with increased terrace width of Si-doped wells. We will discuss the importance of H3SiNH2 doping-reactant formation that gives rise to enhanced decomposition of NH3 and provides wetting conditions by surface Si-N bonds, which reduce the total energy and concentration of NRCs composed of Al vacancies.