Reduction of threading dislocation density in top-down fabricated GaN nanocolumns via their lateral overgrowth by MOCVD

Zubialevich, Vitaly Z.; McLaren, Mathew; Pampili, Pietro; Shen, John; Arredondo, Miryam; Parbrook, P. J.

doi:10.1063/1.5110602

Cited by 9 publications

(4 citation statements)

References 44 publications

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“…An alternative way is to simply reduce the total NC sidewall area (by using low NCs and/or small NC array fill factor) at the same fixed TMGa flow. Just this approach was realized in our recent work 32 where at similar regrowth conditions no reduction in NC height was observed despite this may look counterintuitive at first glance.…”

Section: Nc Regrowthmentioning

confidence: 81%

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Zubialevich

Pampili

Parbrook

2020

Crystal Growth & Design

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Thermal annealing of top−down fabricated GaN nanocolumns (NCs) was investigated over a wide range of temperatures for ammonia-rich atmospheres of both nitrogen and hydrogen. It was found that in contrast to the annealing of planar GaN layers, where surface morphology change is governed purely by material decomposition, reshaping of GaN NCs is strongly affected by competition between different crystallographic facets, which in turn depends on ambient atmosphere and temperature. A qualitative mechanism explaining the observed behavior has been proposed. On the basis of the analysis of these annealing results, growth conditions suitable for either predominantly lateral expansion of the NCs turning their sidewalls into six well-defined vertical m-plane facets, or, vice versa, their infilling from the base regions between the NCs were determined. GaN NC arrays of increased filling factors as compared to the as top−down fabricated ones have been demonstrated using these optimized growth conditions.

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Section: Nc Regrowthmentioning

confidence: 81%

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Zubialevich

Pampili

Parbrook

2020

Crystal Growth & Design

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“…Since III-nitride semiconductor thin films are commonly prepared by growing on substrates which do not match their lattice and thermal expansion coefficient, residual tensile or compressive strain will build up near this interface [39, 40]. Dislocations can form in the film to relax some of this strain [41]. Dislocations that lie at the interface to relieve misfit strain are known as misfit dislocations.…”

Section: Introduction To Iii-nitride Semiconductorsmentioning

confidence: 99%

Uncovering the carrier dynamics of AlInGaN semiconductors using time-resolved cathodoluminescence

Loeto

2022

Materials Science and Technology

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The III-nitride family of semiconductors has proved essential in the design of important optoelectronic technology such as light-emitting diodes (LEDs). To improve our understanding of these materials and their devices it is important to unravel the mysteries of their carrier dynamics. Time-resolved cathodoluminescence (TRCL) is a characterisation technique wherein a pulsed electron beam is used to excite charge carriers in semiconductors. By analysis of the recorded datasets, deductions can be made about the activity of carriers in the period between their generation and recombination. The purpose of this review is to summarise work done on the use of TRCL in the understanding of III-nitride based materials and devices. The focus will be on quantum well LEDs and structural defect-related recombination.

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“…7 We also developed a similar approach with lateral expansion of nanocolumns. 8 Despite the evident success of this approach for Ga-polar materials, there is currently no report of similar techniques for N-polar materials, which is the topic of this Letter. A striking difference between Ga-and N-polar GaN is that, while the former is chemically very stable, the latter can be easily wet-etched in KOH or other hydroxide-containing solutions, which makes this the simplest and most widely used way to discriminate between the two polarities.…”

mentioning

confidence: 99%

“…Examples of this approach in III nitrides are the Facet Initiated Epitaxial Lateral Overgrowth (FIELO) technique, whereby slanted sidewalls occur spontaneously with hydride vapor phase epitaxy (HVPE), and the Facet Controlled Epitaxial Lateral Overgrowth (FACELO) technique, whereby specific growth conditions are needed to induce slanted sidewalls in metal-organic vapor-phase epitaxy (MOVPE) . We also developed a similar approach with lateral expansion of nanocolumns . Despite the evident success of this approach for Ga-polar materials, there is currently no report of similar techniques for N-polar materials, which is the topic of this Letter.…”

mentioning

confidence: 99%

Geometrically Controlled Microscale Patterning and Epitaxial Lateral Overgrowth of Nitrogen-Polar GaN

Pampili,

Zubialevich,

Parbrook

2024

Crystal Growth & Design

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In this Letter, we report on a novel two-step epitaxial growth technique that enables a significant improvement of the crystal quality of nitrogen-polar GaN. The starting material is grown on 4°vicinal sapphire substrates by metal-organic vaporphase epitaxy, with an initial high-temperature sapphire nitridation to control polarity. The material is then converted to a regular array of hexagonal pyramids by wet-etching in a KOH solution and subsequently regrown to coalesce the pyramids back into a smooth layer of improved crystal quality. The key points that enable this technique are the control of the array geometry, obtained by exploiting the anisotropic behavior of the wet-etch step, and the use of regrowth conditions that preserve the orientation of the pyramids' sidewalls. In contrast, growth conditions that cause an excessive expansion of the residual (0001̅ ) facets on the pyramids' tops cause the onset of a very rough surface morphology upon full coalescence. An X-ray diffraction study confirms the reduction of the threading dislocation density as the regrowth step develops. The analysis of the relative position of the 0002̅ GaN peak, with respect to the 0006 sapphire peak, reveals a macroscopic tilt of the pyramids, probably induced by the large off-axis substrate orientation. This tilt correlates very well with an anomalous broadening of the 0002̅ diffraction peaks at the beginning of the regrowth step.

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Reduction of threading dislocation density in top-down fabricated GaN nanocolumns via their lateral overgrowth by MOCVD

Cited by 9 publications

References 44 publications

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Uncovering the carrier dynamics of AlInGaN semiconductors using time-resolved cathodoluminescence

Geometrically Controlled Microscale Patterning and Epitaxial Lateral Overgrowth of Nitrogen-Polar GaN

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