Carrier relaxation dynamics and steady-state charge distributions in coupled InGaN/GaN multiple and single quantum wells

We have examined the carrier capture dynamics and excitation dependent charge distributions of coupled InGaN/GaN multiple quantum well samples. We measured the temporal evolution of time-delayed cathodoluminescence CL spectra to study the temperatureand excitation-dependent transfer of carriers from a surrounding confinement region into a coupled single quantum well. Samples possessing two different structures for the confinement region i.e., number of quantum wells QWs and varying widths were examined with CL. In order to study state filling of the SQW and QWs in the confinement region, we calculated the quasi-Fermi levels and carrier densities by utilizing a model that involves self-consistent solutions of the nonlinear Poisson-Schrödinger equation for wurtzite QWs including strain, deformation potentials, and polarization fields. Band-edge and effective mass parameters were first obtained from a strainand In composition-dependent k ·p calculation for wurtzite InxGa1−xN, using a 6 6 k ·p Hamiltonian in the 0001 representation. The model shows that the difference in the quasi-Fermi levels between the confinement and SQW regions decreases with increasing excitation and temperature. Likewise, a reversal in the relative magnitude of the carrier densities between these two regions occurs at a certain temperature and excitation. Furthermore, the results for the model describing the steady-state excitation are consistent with those for the transient excitation in time-resolved CL, which also exhibit a marked increase in the rate of carrier transfer to the SQW region as the temperature increases. © 2007 American Institute of Physics. DOI: 10.1063/1.2727437