Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence.

Thomas F K Weatherley,Duncan T L Alexander,Vitaly Osokin,Jean-François Carlin,Nicolas Grandjean,Robert A Taylor,Wei Liu,Raphaël Butté

doi:10.1021/acs.nanolett.1c01295

Thomas F K Weatherley, Duncan T L Alexander + Show 6 more

Open Access

https://doi.org/10.1021/acs.nanolett.1c01295

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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 nonradiative 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 analyze nonradiative PDs in InGaN/GaN QWs at the nanoscale. We identify two different types of PDs by their contrasting behavior with temperature and measure their densities from 1014 cm-3 to as high as 1016 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 nonradiative behavior of PDs. The results in this study are readily interpreted directly from CL images and represent a significant advancement in nanoscale PD analysis.

Highlights

Crystallographic point defects (PDs) can dramatically decrease the efficiency of optoelectronic semiconductor devices, many of which are based on quantum well (QW) heterostructures
It is more common for PD recombination to proceed via multiplephonon emission resulting in no light emission at all,[5] and such nonradiative PDs can dramatically decrease the internal quantum efficiency (IQE) of optoelectronic devices such as light-emitting diodes (LEDs), laser diodes, and solar cells.[6−8]
The critical role of nonradiative PDs in QWs is exemplified perfectly by III-nitride semiconductors: recent literature indicates that an intrinsic PD in InGaN/GaN QWs acts as a highly effective nonradiative recombination center, killing the IQE of green to near-ultraviolet LEDs.[17−21] These PDs arise during growth from an initial population of GaN surface defects which are only incorporated into layers with indium content.[21,22]

Summary

Introduction

Crystallographic point defects (PDs) can dramatically decrease the efficiency of optoelectronic semiconductor devices, many of which are based on quantum well (QW) heterostructures. Upon cooling to 10 K (Figure 2k−o), the impact from PDs is noticeably suppressed, as expected since the reduction in diffusion length means fewer carriers can reach PDs. Nonradiative recombination at defects usually requires multiple-phonon emission, which is less likely at low temperatures.[5] we still see some influence of PDs on the QW intensity.

Results

Conclusion