Characterization of InGaN/GaN quantum well growth using monochromated valence electron energy loss spectroscopy

Pališaitis, Justinas; Lundskog, Anders; Forsberg, Urban; Janzén, Erik; Birch, Jens; Hultman, Lars; Persson, Per

doi:10.1063/1.4861179

Cited by 3 publications

(2 citation statements)

References 36 publications

(32 reference statements)

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“…The formation of these wider inhomogeneities is always detected at the upper QW interface, which is typically rougher than the lower one, in good agreement with the previous observations for similar systems. 14,39,40 In these images, the bright Z-contrast is indicative of the substitution of lighter gallium atoms for heavier indium ones. As the layers grow epitaxially, keeping the wurtzite structure, we expect a certain level of strain to be present in the crystalline structure.…”

Section: Qw Structural Examination and Strain Analysis: High Resoluti...mentioning

confidence: 95%

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Quantitative parameters for the examination of InGaN QW multilayers by low-loss EELS

Eljarrat

López‐Conesa

Magén

et al. 2016

Phys. Chem. Chem. Phys.

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We present a detailed examination of a multiple InxGa1-xN quantum well (QW) structure for optoelectronic applications. The characterization is carried out using scanning transmission electron microscopy (STEM), combining high-angle annular dark field (HAADF) imaging and electron energy loss spectroscopy (EELS). Fluctuations in the QW thickness and composition are observed in atomic resolution images. The impact of these small changes on the electronic properties of the semiconductor material is measured through spatially localized low-loss EELS, obtaining band gap and plasmon energy values. Because of the small size of the InGaN QW layers additional effects hinder the analysis. Hence, additional parameters were explored, which can be assessed using the same EELS data and give further information. For instance, plasmon width was studied using a model-based fit approach to the plasmon peak; observing a broadening of this peak can be related to the chemical and structural inhomogeneity in the InGaN QW layers. Additionally, Kramers-Kronig analysis (KKA) was used to calculate the complex dielectric function (CDF) from the EELS spectrum images (SIs). After this analysis, the electron effective mass and the sample absolute thickness were obtained, and an alternative method for the assessment of plasmon energy was demonstrated. Also after KKA, the normalization of the energy-loss spectrum allows us to analyze the Ga 3d transition, which provides additional chemical information at great spatial resolution. Each one of these methods is presented in this work together with a critical discussion of their advantages and drawbacks.

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Section: Qw Structural Examination and Strain Analysis: High Resoluti...mentioning

confidence: 95%

“…Note that while the ZLP carries little chemical information, the plasmon peak is directly related to the composition of the material and has been exploited in group-III nitride compound semiconductors. [12][13][14][15][16] Fig. 1a shows a typical low-loss EELS spectrum from In x Ga 1Àx N, which includes the mentioned features.…”

Section: Theoretical Backgroundmentioning

confidence: 99%