Revisiting the “In-clustering” question in InGaN through the use of aberration-corrected electron microscopy below the knock-on threshold

Abstract

The high intensity of light emitted in In x Ga 1Àx N/GaN heterostructures has been generally attributed to the formation of indium-rich clusters in In x Ga 1Àx N quantum wells (QWs). However, there is significant disagreement about the existence of such clusters in as-grown In x Ga 1Àx N QWs. We employ atomically resolved C S-corrected scanning transmission electron microscopy and electron energy loss spectroscopy at 120 kV-which we demonstrate to be below the knock-on displacement threshold-and show that indium clustering is not present in as-grown In 0.22 Ga 0.78 N QWs. This artifact-free, atomically resolved method can be employed for investigating compositional variations in other In x Ga 1Àx N/GaN heterostructures. V

X‐ray reflectivity method for the characterization of InGaN/GaN quantum well interface

“…However until now, this was done using transmission electron microscopy (TEM) or atom probe tomography (APT) . However these methods are time‐consuming, destructive, and can be experimentally challenging when beam damage of the QWs is taken into consideration.…”

Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

“…Following the experimental data in Refs. [46][47][48][49][50][51], we treat InGaN as a random alloy. To realize different microscopic configurations, our calculations have been repeated ten times with changing the atomic distribution.…”

Instrumental requirements for the detection of electron beam-induced object excitations at the single atom level in high-resolution transmission electron microscopy

“…In fact, maintaining a pristine object structure during an image acquisition is known to be essential and considered an "art". If abandoned it can lead to seemingly endless debates about the "true" atomic structure of matter (Smeeton et al, 2003) as it is the case for reports on the indium cluster formation in InGaN (Smeeton et al, 2003;Bartel et al, 2007;Baloch et al, 2013;Kisielowski, 2013). The underlying beam-sample interactions are most obvious if small nanocrystals are observed (Smith et al, 1986).…”

“…Unfortunately, it is a persistent misconception that bulk binding energies are relevant in such processes if acceleration voltages between 80 kV and 300 kV are used (e.g. Baloch et al, 2013).…”