Photoluminescence of GaN quantum dots in AlN matrix

In the present work steady-state and time-resolved photoluminescence (PL) from self-assembled GaN quantum dots (QDs) embedded in AlN matrix has been studied. The maximum of low-temperature PL is near 2.55 eV that is below the band gap of bulk GaN. The PL peak is not shifted with variation of excitation power. When temperature is increasing the PL peak exhibits a red shift in accordance with a temperature dependence of the band gap of bulk GaN. A huge red shift of the PL maximum from 3.0 down to 2.2 eV is observed as a function of the delay time after the excitation pulse. The PL decay is non-exponential and spectral dependent. The PL decay time varies from about 10 μs to more than 100 μs over the spectrum. The experimental results interpreted in framework of a model taking into account an internal electric field in QDs and transport of the non-equilibrium carriers between QDs.