Critical impact of Ehrlich–Schwöbel barrier on GaN surface morphology during homoepitaxial growth

Kaufmann, Nils Asmus Kristian; Lahourcade, Lise; Hourahine, B.; Martin, D.; Grandjean, N.

doi:10.1016/j.jcrysgro.2015.06.013

Cited by 69 publications

(71 citation statements)

References 48 publications

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“…In fact, this morphology stems from the deposition of a few tens of nanometers of GaN at LT before the deposition of InGaN epilayers, which leads to surface roughening induced by the presence of an EhrlichSchw€ obel barrier (ESB). 35 In addition, surface morphology images also reveal a much shorter range disorder inherent to the InGaN epilayers, which manifests itself by a spectral broadening in the SNOM spectra above the random alloy limit and is reminiscent of an ESB-induced surface roughening of the InGaN layer itself. Here, the related variations in the local step-edge density should likely affect the …”

Section: à2mentioning

confidence: 99%

Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations

Butté

Lahourcade

Uždavinys

et al. 2018

Applied Physics Letters

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To assess the impact of random alloying on the optical properties of the InGaN alloy, high-quality InxGa1−xN (0 < x < 0.18) epilayers grown on c-plane free-standing GaN substrates are characterized both structurally and optically. The thickness (25–100 nm) was adjusted to keep these layers pseudomorphically strained over the whole range of explored indium content as checked by x-ray diffraction measurements. The evolution of the low temperature optical absorption (OA) edge linewidth as a function of absorption energy, and hence the indium content, is analyzed in the framework of the random alloy model. The latter shows that the OA edge linewidth should not markedly increase above an indium content of 4%, varying from 17 meV to 30 meV for 20% indium. The experimental data initially follow the same trend with, however, a deviation from this model for indium contents exceeding only ∼2%. Complementary room temperature near-field photoluminescence measurements carried out using a scanning near-field optical microscope combined with simultaneous surface morphology mappings reveal spatial disorder due to growth meandering. We conclude that for thick high-quality pseudomorphic InGaN layers, a deviation from pure random alloying occurs due to the interplay between indium incorporation and longer range fluctuations induced by the InGaN step-meandering growth mode.

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Section: à2mentioning

confidence: 99%

Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations

Butté

Lahourcade

Uždavinys

et al. 2018

Applied Physics Letters

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“…Figure 2 displays maps of the surface morphology, its gradient in the horizontal direction, and PL peak energy. The morphology map and large area scans [21] indicate that the surface is covered by large undulations that are parallel to the miscut direction and laterally spread over tens to hundreds of µm. The undulations are observed on samples with and without the InGaN layer, i.e.…”

Section: Spectrally-resolved Snom Applied On Ingan Epitaxial Layersmentioning

confidence: 99%

“…they originate from the GaN template. They emerge during the step-flow growth due to step meandering that occurs because of the EhrlichSchwöbel barrier for adatom movement down the monolayer steps [21].…”

Section: Spectrally-resolved Snom Applied On Ingan Epitaxial Layersmentioning

confidence: 99%

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Multimode scanning near-field photoluminescence spectroscopy and its application for studies of InGaN epitaxial layers and quantum wells

Marcinkevičius¹,

Uždavinys²,

Ivanov³

et al. 2018

physics

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The paper reviews our recent achievements in developing a multimode scanning near-field optical microscopy (SNOM) technique. The multimode SNOM apparatus allows us to simultaneously measure spatial variations of photoluminescence spectra in the illumination and illumination-collection modes, their transients and sample surface morphology. The potential of this technique has been demonstrated on a polar InGaN epitaxial layer and nonpolar InGaN/GaN quantum wells. SNOM measurements have allowed revealing a number of phenomena, such as the band potential fluctuations and their correlation to the surface morphology, spatial nonuniformity of the radiative and nonradiative lifetimes, as well as the extended band nature of localized states. The combination of different modes enabled measurements of the ambipolar carrier diffusion and its anisotropy.

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“…[10][11][12][13] This work will evaluate GaN films grown by MOCVD on HVPE substrates to understand the impact of surface roughness on Shcottky barrier diode performance to evaluate metrics for evaluating epitaxial layer quality and uniformity.…”

mentioning

confidence: 99%

Effect of Surface Morphology on Diode Performance in Vertical GaN Schottky Diodes

Hite

Anderson

Mastro

et al. 2017

ECS J. Solid State Sci. Technol.

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The properties of thick GaN layers grown by metal organic chemical vapor deposition on 2 HVPE substrates were investigated. Although the epilayer is smooth on a microscopic scale with high quality layers as evidenced by X-ray diffraction and photoluminescence, macroscopic morphological variations are observed on the wafer surface. These variations correspond to disparities in leakage current in fabricated Schottky barrier diodes, with rougher macroscopic morphology resulting in increased leakage current. GaN-based technology has found widespread success in the electronic and optoelectronic fields, both as transistors and LEDs.1-3 These successes are mainly based on lateral device geometries or thin vertical structures based on heteroepitaxy on non-native substrates. While monolithic microwave integrated circuits (MMICs) based on high electron mobility transistor (HEMT) structures have enjoyed great success as RF power amplifiers, the lateral device geometry presents fundamental limitations, particularly for breakdown voltage, thus limiting applications for high power switching. [4][5][6][7][8] To overcome some of these limitations and reach the full potential of the material for power devices, the next-generation of GaN power switching devices needs to move to a vertical geometry, which is enabled by the commercial availability of high quality, freestanding GaN substrates produced by hydride vapor phase epitaxy (HVPE) or ammonothermal growth. 9Homoepitaxial growth of power device quality GaN films on native substrates presents unique challenges from preparing the surface for growth, both to remove impurities and reduce thermal decomposition, to reducing impurities in the film for thick drift layers. [10][11][12][13] This work will evaluate GaN films grown by MOCVD on HVPE substrates to understand the impact of surface roughness on Shcottky barrier diode performance to evaluate metrics for evaluating epitaxial layer quality and uniformity.The samples in this study were grown in an Emcore D-180 metal organic chemical vapor deposition (MOCVD) reactor on a commercially-sourced, 2 freestanding n+ GaN substrate from Kyma Technologies grown by HVPE. The MOCVD growth consisted of 5 μm of unintentionally doped GaN using standard growth conditions (3000 V/III, 200 Torr, 1030• C) and precursors (trimethylgallium and ammonia). Secondary ion mass spectroscopy (SIMS) measurements on films from this reactor under these growth conditions indicate background oxygen and carbon impurities at detection limits and a Si concentration of ∼2 × 10 16 cm −3 . As the substrate was received polished to an epi-ready surface, no additional in-situ or ex-situ cleaning procedures were undertaken. After growth, the surface morphology was characterized using multiple techniques to evaluate many length scales, including optical microscopy, atomic force microscopy (AFM), and optical profilometry. In addition, photoluminescence (PL), X-ray diffraction (XRD), and wafer bow were investigated to assess material quality.XRD maps were taken of the wafer...

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Critical impact of Ehrlich–Schwöbel barrier on GaN surface morphology during homoepitaxial growth

Cited by 69 publications

References 48 publications

Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations

Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations

Multimode scanning near-field photoluminescence spectroscopy and its application for studies of InGaN epitaxial layers and quantum wells

Effect of Surface Morphology on Diode Performance in Vertical GaN Schottky Diodes

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