The influence of defects and piezoelectric fields on the luminescence from InGaN/GaN single quantum wells

High spatial resolution cathodoluminescence (CL) studies have been carried out on GaN/InGaN/(0001)GaN single quantum well (SQW) structures in a field emission scanning electron microscope at 5kV and temperatures down to 8K. Direct comparison of QW CL maps with transmission electron microscope studies of plan-view samples showed that edge type threading dislocations act as non-radiative recombination centers. Spectra taken from extended areas showed a progressive blue shift in the QW emission from around 460nm at low beam intensities to about 445nm as the beam intensity was increased. This effect which correlated with a decrease in the spatial resolution is interpreted as due to an increase in the diffusion length of carriers in the SQW due to a combination of screening of the piezoelectric field and band filling effects