Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

He, Chenguang; Qin, Zhixin; Xu, Fujun; Zhang, Lisheng; Wang, Jiaming; Hou, Mengjun; Zhang, Shan; Wang, Xinqiang; Ge, Weikun; Shen, Bo

doi:10.1038/srep25124

Cited by 28 publications

(24 citation statements)

References 22 publications

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“…We speculate that the redshift of the QW emission is due to the increased incorporation of Ga on a relaxed AlGaN layer. Indeed, similar compositional increase was reported for a relaxed AlGaN . The observed PL shift is equivalent to a compositional change of 0.05 for the full relaxation, given that the QW width is constant.…”

Section: Resultssupporting

confidence: 82%

Influence of the Strain Relaxation on the Optical Property of AlGaN Quantum Wells

Itokazu

Mogami

Kuwaba

et al. 2020

Physica Status Solidi (b)

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The influence of strain relaxation on the optical properties of AlGaN quantum wells (QWs) is investigated. The relaxation ratio is controlled by changing the thickness of an AlGaN buffer layer. The relaxation ratio increases from 20% to 100% with increasing the AlGaN layer thickness from 0.5 to 6.0 μm. Photoluminescence (PL) intensity reaches maximum at a relaxation ratio of 36%, which implies competing effects in radiative and nonradiative recombinations. From the viewpoint of radiative recombination, strain relaxation increases the polarization field in the QW, which decreases the electron–hole overlap. The observed gradual decrease in PL may come from this effect. In terms of nonradiative recombination, the dislocation density is nearly constant up to 4.5 μm from the AlN/AlGaN interface, and decreases at 6.0 μm. Therefore, it is difficult to explain the observed PL intensity by the dislocation‐related nonradiative pathways. Instead, relieved strain can decrease the point‐defect density. Strain relaxation can reduce the vacancy concentration as a result of increased formation energy with the partial relief of compressive strain. The effect of strain on the band structure change is also discussed, where the relieved compressive strain increases the crystal‐field split‐off component in the valence band maximum, resulting in a decreased PL intensity.

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Section: Resultssupporting

confidence: 82%

Influence of the Strain Relaxation on the Optical Property of AlGaN Quantum Wells

Itokazu

Mogami

Kuwaba

et al. 2020

Physica Status Solidi (b)

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“…One potential mechanism is the Al pulling effect similar to the In pulling effect in InGaN layers grown on GaN [28][29][30] . Different nucleation conditions as used in our work were shown to induce different depth profiles of the grown-in V-pit density, which in turn has an influence on stress relaxation and thus on Al incorporation 3,24,30,31 .…”

Section: Leakage Current and Relation To Dislocation Types As Mentiomentioning

confidence: 86%

The impact of dislocations on AlGaN/GaN Schottky diodes and on gate failure of high electron mobility transistors

Besendörfer

Meissner

Medjdoub

et al. 2020

Sci Rep

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GaN epitaxially grown on Si is a material for power electronics that intrinsically shows a high density of dislocations. We show by Conductive Atomic Force Microscopy (C-AFM) and Defect Selective Etching that even for materials with similar total dislocation densities substantially different subsets of dislocations with screw component act as current leakage paths within the AlGaN barrier under forward bias. Potential reasons are discussed and it will be directly shown by an innovative experiment that current voltage forward characteristics of AlGaN/GaN Schottky diodes shift to lower absolute voltages when such dislocations are present within the device. A local lowering of the Schottky barrier height around conductive dislocations is identified and impurity segregation is assumed as responsible root cause. While dislocation related leakage current under low reverse bias could not be resolved, breakdown of AlGaN/GaN Schottky diodes under high reverse bias correlates well with observed conductive dislocations as measured by C-AFM. If such dislocations are located near the drain side of the gate edge, failure of the gate in terms of breakdown or formation of percolation paths is observed for AlGaN/GaN high electron mobility transistors.

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“…The observed self‐organized compositional pulling during SL growth is known from the highly mismatched AlGaN wells on AlN or GaN templates [ 25 ] and even in pseudomorphic distributed Bragg reflectors, [ 26–28 ] if the gallium content is high, i.e., if there is strong compressive stress. One common explanation was that gallium adatoms with their large atomic radius are rejected at the growth front to minimize compressive stress.…”

Section: Resultsmentioning

confidence: 99%

Improved Efficiency of Ultraviolet B Light‐Emitting Diodes with Optimized p‐Side

Kolbe

Knauer

Raß

et al. 2020

Physica Status Solidi (a)

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Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

Cited by 28 publications

References 22 publications

Influence of the Strain Relaxation on the Optical Property of AlGaN Quantum Wells

Influence of the Strain Relaxation on the Optical Property of AlGaN Quantum Wells

The impact of dislocations on AlGaN/GaN Schottky diodes and on gate failure of high electron mobility transistors

Improved Efficiency of Ultraviolet B Light‐Emitting Diodes with Optimized p‐Side

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