Imaging non-radiative point defects buried in quantum wells using cathodoluminescence

TL;DR

This study demonstrates high-resolution cathodoluminescence imaging to spatially resolve and analyze non-radiative point defects in buried quantum wells, revealing their types, densities, and effects on carrier dynamics.

Contribution

It introduces a novel method combining high-resolution CL and specific sample design to image and analyze non-radiative point defects in quantum wells, a feat not previously achieved.

Findings

Identified two types of point defects based on temperature behaviour.

Measured defect densities ranging from 10^{14} to 10^{16} cm^{-3}.

Showed how defect concentration affects carrier diffusion and non-radiative behaviour.

Abstract

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.