Quantum-structure-dependent excitonic carrier dynamics of in _xGa_1-xN/GaN multi-quantum-wells

The excitonic carrier dynamics taking place in In_xGa _1-xN/GaN multi-quantum-well systems have been studied by using low temperature picosecond-time-resolved photoluminescence (LT-TRPL), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Dynamic time of flight secondary ion mass spectrometry (TOF-SIMS), and quantum mechanical simulation methods. Both time-integrated and time-resolved photoluminescence spectra of In_xGa_1-xN/GaN multi-quantum-wells with different well thicknesses and indium compositions were measured at 10 K. We assigned the natural radiative lifetime of each sample from the time-resolved PL. We observed that the natural radiative lifetime of In In_xGa_1-xN/GaN multi-quantum-wells depended strongly on the well thickness and the indium composition. To support the measured natural radiative lifetimes, we calculated the excitonic oscillator strengths of the In_xGa_1-xN/GaN multi-quantum-wells as functions of well thickness and indium composition by using a 2-D particle-in-a-box model. Values of the well thicknesses and indium compositions from the HR-TEM and XPS compositional depth profiling were used to achieve more realistic computational results and to corroborate the measured natural radiative lifetimes of In _xGa_1-xN/GaN multi-quantum wells.