Revealing extended defects in HVPE-grown GaN

Weyher, J.L.; Łucznik, B.; Grzegory, I.; Smalc-Koziorοwska, Julita; Paskova, T.

doi:10.1016/j.jcrysgro.2010.04.021

Cited by 28 publications

(31 citation statements)

References 13 publications

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“…All these results clearly showed that a GaN epitaxial layer with a device-quality smooth as-grown surface and a good thickness uniformity, comparable to that produced by the MOCVD method, can be obtained by the HVPE method, contrary to the beliefs regarding HVPE growth that are commonly held among the GaN material community. [30][31][32][33][34] HVPE growth on freestanding GaN substrates produced surfaces of a similar quality. As examples, a DIC surface image and an AFM image of unintentionally doped GaN layers grown by the HVPE method are shown in Figs.…”

Section: Resultsmentioning

confidence: 84%

“…However, only a few attempts have been made to apply this technique, probably because of widely held beliefs regarding the drawbacks of the HVPE method, such as the high background donor concentrations (resulting from residual Si and O, instead of C) 17,23) and difficulties in producing smooth as-grown surfaces [30][31][32] and uniform thickness, as required for device structures. 33,34) Even for high-crystalline-quality GaN crystals grown by HVPE, residual donor concentrations from 10 15 to 10 17 cm −3…”

Section: Introductionmentioning

confidence: 99%

“…35,36) Roughening of GaN surfaces by pits and hillocks is often observed in HVPE-grown materials. [30][31][32] Difficulties in achieving a uniform thickness by HVPE growth have been also reported. 33,34) However, these problems have not previously been regarded as serious, because the aim of earlier HVPE studies was to fabricate freestanding single crystals of GaN whose surface roughness and thickness nonuniformity could be removed by a subsequent polishing process.…”

Section: Introductionmentioning

confidence: 99%

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Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Fujikura

Konno

Yoshida

et al. 2017

Jpn. J. Appl. Phys.

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Thick (20–30 µm) layers of highly pure GaN with device-quality smooth as-grown surfaces were prepared on freestanding GaN substrates by using our advanced hydride-vapor-phase epitaxy (HVPE) system. Removal of quartz parts from the HVPE system markedly reduced concentrations of residual impurities to below the limits of detection by secondary-ion mass spectrometry. Appropriate gas-flow management in the HVPE system realized device-quality, smooth, as-grown surfaces with an excellent uniformity of thickness. The undoped GaN layer showed insulating properties. By Si doping, the electron concentration could be controlled over a wide range, down to 2 × 1014 cm−3, with a maximum mobility of 1150 cm2·V−1·s−1. The concentration of residual deep levels in lightly Si-doped layers was in the 1014 cm−3 range or less throughout the entire 2-in. wafer surface. These achievements clearly demonstrate the potential of HVPE as a tool for epitaxial growth of power-device structures.

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Section: Resultsmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Fujikura

Konno

Yoshida

et al. 2017

Jpn. J. Appl. Phys.

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“…The spatial modulation of doping levels may be caused by the quasi-periodic change in the direction of growth. As suggested by Weyher et al 17 the growth in well-defined crystallographic direction, e.g. in [10][11] direction with the (10-12) interface, is replaced by the growth in variable direction with clear growth striations.…”

Section: Ecs Journal Of Solid State Science and Technology 5 (5) P21mentioning

confidence: 99%

“…The investigations of GaN substrates subjected to photo-chemical etching indicated relatively fine modulation of the electrical and optical properties, both in-depth and in-plane directions, within extended areas covered by the overgrown V-shaped defects or pits. [16][17][18] In particular, micro-cathodoluminescence mapping revealed circular regions with relatively high emission intensity on both Ga-and N-faces of HVPE-grown GaN substrates.12,14 According to data in the literature, 17,18 the islands between circular regions are characterized by lower intensity band-edge luminescence and lower free carrier concentration. The available data, however, are fragmentary and do not add up to an accurate and complete picture regarding in-plane and in-depth variations of the electrical and emission characteristics, and their dependence upon the substrate polarity.…”

mentioning

confidence: 99%

Self-Organized Three-Dimensional Nanostructured Architectures in Bulk GaN Generated by Spatial Modulation of Doping

Tiginyanu

Stevens‐Kalceff

Sarua

et al. 2016

ECS J. Solid State Sci. Technol.

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Self-organized 3D nanostructured architectures including quasi-ordered concentric hexagonal structures generated during the growth of single crystalline n-GaN substrates by hydride vapor phase epitaxy (HVPE) are reported. The study of as-grown samples by using Kelvin Probe Force Microscopy shows that the formation of self-organized architectures can be attributed to fine modulation of doping related to the spatial distribution of impurities. The specific features of nanostructured architectures involved have been brought to light by using electrochemical and photoelectrochemical etching techniques which are highly sensitive to local doping. The analysis of the results shows that the formation of self-organized spatial architectures in the process of HVPE is caused by the generation of V-pits and their subsequent overgrowth accompanied by the growth in variable direction. It is demonstrated for the first time that the electrical and luminescence properties of HVPE-grown GaN are spatially modulated throughout, including islands between overgrown V-pit regions. The dependence of doping upon growth direction is confirmed by the micro-cathodoluminescence characterization of HVPE-grown pencil-like microcrystals exposing various crystallographic planes along the tip. These results are indicative of new possibilities for defect engineering in gallium nitride and for three-dimensional spatial nanostructuring of this important electronic material by controlling the growth direction. Gallium Nitride (GaN), a wide-bandgap semiconductor compound (E g = 3.4 eV at 300 K), is considered nowadays the second most important semiconductor material after Si. Over the past decades it has played a major role in the development of modern solid-state lighting industry.1-3 An intensive investigation of this compound started in 1970's, but with minimal success in the development of real applications. In the absence of native bulk material, GaN epilayers were grown on foreign substrates and, as a result of the large lattice mismatch and difference in thermal expansion coefficients, the overgrown films contained a high concentration of threading dislocations. The fascinating point, however, is that even in the presence of very high concentrations of dislocations, sometimes exceeding 10 10 cm −2 , gallium nitride exhibits intense luminescence, a property that makes the compound unique in comparison with other III-V materials, such as GaAs, GaP and InP. This particular feature along with other material characteristics were of paramount importance for the development and subsequent commercialization of GaN-based blue light emitting diodes by the mid-1990s. 4 This significant optoelectronic success resulted in the Nobel Prize for Physics being awarded to Shuji Nakamura, Isamu Akasaki and Hiroshi Amano, in 2014. There is no doubt that lighting technologies based on GaN and related nitrides will continue their impactful evolution, particularly in view of the recent demonstration of electrically pumped inversionless polariton lasing at room temper...

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Defect sensitive etching of nitrides: appraisal of methods

Weyher

2011

Cryst. Res. Technol.

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Defect selective etching methods used for structural characterization of nitrides (GaN, AlGaN, InGaN and AlN) single crystals and epitaxial layers are summarized. The mechanism of surface reactions during orthodox chemical etching and photoetching is briefly described. Examples of defects which can be revealed mainly in bulk and epitaxial GaN using different etching systems are shown together with schematic models of defects. Special attention is given to selective etching and analysis of complex electrically active non‐homogeneities in bulk and HVPE‐grown GaN, which show up as areas of different etch rate, i.e. different carrier concentration. These defects are clearly visible after photo‐etching on both Ga‐polar surface and on any non‐polar cleavage plane. Ultra high selectivity of electroless photoetching on electrically active defects is explained by separation of photocurrent‐potential plots of areas with different carrier concentration. Formation of nano‐pillars on dislocations during photoetching is explained by recombinative properties of linear defects for photo‐generated carriers. Special applications of defect‐selective etching methods for (i) nano‐patterning of GaN surface for preparing highly efficient platforms for surface enhanced Raman spectroscopy (SERS) measurements and (ii) overgrowth of deep etch pits for reduction of dislocation density during HVPE growth of thick GaN crystals is also demonstrated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Revealing extended defects in HVPE-grown GaN

Cited by 28 publications

References 13 publications

Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Self-Organized Three-Dimensional Nanostructured Architectures in Bulk GaN Generated by Spatial Modulation of Doping

Defect sensitive etching of nitrides: appraisal of methods

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