  Crystallographic point defects (PDs) can dramatically decrease the efficiency
of optoelectronic semiconductor devices, many of which are based on quantum
well (QW) heterostructures. However, spatially resolving individual
non-radiative PDs buried in such QWs has so far not been demonstrated. Here,
using high-resolution cathodoluminescence (CL) and a specific sample design, we
spatially resolve, image, and analyse non-radiative PDs in InGaN/GaN QWs. We
identify two different types of PD by their contrasting behaviour with
temperature, and measure their densities from $10^{14}$ cm$^{-3}$ to as high as
$10^{16}$ cm$^{-3}$. Our CL images clearly illustrate the interplay between PDs
and carrier dynamics in the well: increasing PD concentration severely limits
carrier diffusion lengths, while a higher carrier density suppresses the
non-radiative behaviour of PDs. The results in this study are readily
interpreted directly from CL images, and represent a significant advancement in
nanoscale PD analysis.
