Photoluminescence of GaN quantum wells with AlGaN barriers of high aluminium content

We report photoluminescence and time-resolved photoluminescence measurement s of GaN multiple quantum wells (QWs) with AlxGa1-xN barriers of high alumi nium content. GaN/Al0.8Ga0.2N samples were grown with well widths as low as one monolayer, giving photoluminescence of peak energy 5.03 eV (247 nm) at room temperature. A study of lifetimes in GaN/Al0.5Ga0.5N samples shows lo w temperature recombination to be dominated by radiative processes with lif etimes approximate to 0.5 ns in 1 to 2 nm wells. Dependence of lifetime on emission energy is very small compared to InGaN QWs, indicating that carrie r localization is very slight and interface quality is high. In 4 nm wells, PL emission at an energy below the bulk GaN band gap and long recombinatio n lifetimes result from the polarization field across the wells.