Alloy segregation at stacking faults in zincblende GaN heterostructures

B Ding,A Kovács,M Frentrup,M Jain,R A Oliver,S M Fairclough,D J Wallis,M J Kappers

doi:10.1063/5.0015157

Abstract

Current cubic zincblende III-Nitride epilayers grown on 3C-SiC/Si(001) substrates by metal-organic vapor-phase epitaxy contain a high density of stacking faults lying on the {111} planes. A combination of high-resolution scanning transmission electron microscopy and energy dispersive x-ray spectrometry is used to investigate the effects of alloy segregation around stacking faults in a zincblende III-nitride light-emitting structure, incorporating InGaN quantum wells and an AlGaN electron blocking layer. It is found that in the vicinity of the stacking faults, the indium and aluminum contents were a factor of 2.3 ± 1.3 and 1.9 ± 0.5 higher, respectively, than that in the surrounding material. Indium and aluminum are also observed to segregate differently in relation to stacking faults with indium segregating adjacent to the stacking fault while aluminum segregates directly on the stacking fault.

Highlights

Despite the commercially successful rise of GaN-based optoelectronics over the last two decades, the so-called “green gap” problem1 remains unsolved to date
A combination of high-resolution scanning transmission electron microscopy and energy dispersive x-ray spectrometry is used to investigate the effects of alloy segregation around stacking faults in a zincblende III-nitride light-emitting structure, incorporating InGaN quantum wells and an AlGaN electron blocking layer
Segregation of alloying elements around SFs in GaN-based materials has not been widely reported in the literature but it has been observed in materials such as brass alloys, where this phenomenon is referred to as Suzuki segregation

Summary

Introduction

Despite the commercially successful rise of GaN-based optoelectronics over the last two decades, the so-called “green gap” problem remains unsolved to date. The term refers to the sharp drop in quantum efficiency for InGaN-based emitters at longer wavelengths beyond the blue spectral range.. Approaching the green spectral range from the red side using arsenide and phosphide-based III-V compounds proves frustrating.. While the scientific debate on the origin of this efficiency problem in InGaN-based emitters is continuing, the focus is on factors affecting the radiative and nonradiative recombination processes, in particular, carrier localization at alloy fluctuations in InGaN alloys, the increase in lattice-mismatch induced strain, and reductions in material quality with the increasing InN fraction employed to reach longer wavelengths.. A potential strategy to avoid such problems, which are related to intrinsic properties of wurtzite c-plane heterostructures, is the application of the nonpolar zincblende (zb) phase.

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Discussion

Conclusion