Hardness control for improvement of dislocation reduction in HVPE-grown freestanding GaN substrates

Fujikura, Hajime; Oshima, Yuki; Megro, Takeshi; Saito, Toshiya

doi:10.1016/j.jcrysgro.2011.12.019

Cited by 18 publications

(19 citation statements)

References 20 publications

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“…The GaN wafers were grown using hypride vapor phase epitaxy (HVPE) technique. The details of growth procedures in preparing these GaN can be found elsewhere [20][21][22]. Then exfoliated GaN nanomembranes were transferred mechanically by lifting them with a 40 nm thick tungsten probe then place them on a sapphire substrate [20].…”

Section: Methodsmentioning

confidence: 99%

Nanoindentation Induced Elastic-plastic Deformation of GaN Nanomembrane on a Sapphire Substrate

Khayyat

Bourhis

ElAfandy³

et al. 2021

AJN

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One of the main challenges of the production of a blue laser is the preparation of defect-free GaN layers. It is of high tehnological interest to characterize GaN nanomembrane mechanically for further advanced applications. The current study addresses the impact of applied stresses on GaN nanomembranes, which are placed on sapphire the substrates, using nanoindentation as a nondestructive test. The mechanical response of the 20, and 100 nm thin GaN nanomembrane were studied at different normal applied loads ranging from 1 mN down to 0.1 mN using the Berkovich nanoindentation technique. There were plastic deformation regions at the nanoindented GaN nanomembranes monitored by the load-displacement (p-h) curves. The depth of the deformed regions increased with increasing the applied loads on the diamond indenter. Beside the insitu depth estimation of the residual nanoindentation using the instrumented nanoindentation machine, Atomic Force Microscopy (AFM) has been deployed as an ex-situ measurements of indentations depth. Scanning Electron Microscopy (SEM) provided us with surface images of the indented membranes. Indentation of the 100 nm thick GaN nanomembrane, where the effect of the substrate is reduced, showed discontinuity in the p-h curves. These discontinuity or pop-in events were attributed to a possible sudden initiation and propagation of threading dislocations in the GaN nanomembrane which was free of threading dislocation upon fabrication. It was suggested to employ µ-Raman spectroscopy methods to investigate the possible structural phase transformation of thicker GaN nanomembranes and to measure the compressive or tensile stresses within the center of the indented zones. Where the observed sudden load-displacements discontinuity or depth excursions during indentation of GaN nanomembranes can be attributed.

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Section: Methodsmentioning

confidence: 99%

Nanoindentation Induced Elastic-plastic Deformation of GaN Nanomembrane on a Sapphire Substrate

Khayyat

Bourhis

ElAfandy³

et al. 2021

AJN

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“…In order to achieve such ideal GaN crystals, various growth techniques-such as the hydride vapor phase epitaxy (HVPE) method, the ammonothermal method, or a combination of both-have been studied by many researchers. [8][9][10][11][12][13] We also attempted HVPE homoepitaxial thick growth on a seed GaN wafer produced with a multi-point-seed (MPS) technique by the Na-flux method. 14) Large-diameter (>2″) GaN wafers with low TDD on the order of 10 3 -10 5 cm −2 could be obtained after the coalescence of crystals grown from individual small seeds.…”

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confidence: 99%

Anomalous dislocation annihilation behavior observed in a GaN crystal grown on point seeds by the Na-flux method

Imanishi

Okumura

Nakamura

et al. 2020

Appl. Phys. Express

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We recently invented a method called the flux-film-coated technique for purifying a GaN wafer with low dislocation density grown from point-seed crystals. In this study, we investigated the mechanism behind the reduction of dislocation density in the GaN wafer by evaluating the three-dimensional behavior of dislocations using multiphoton-excitation photoluminescence images. We made the surprising discovery that dislocations more than 50 μm away disappeared by annihilating each other as growth proceeded, and this is one of the mechanisms underlying the dislocation density reduction. The moving distance of dislocations before annihilation is uncommon and a unique phenomenon in the Na-flux method.

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“…The performance of early GaN-based power devices, which were made on foreign substrates, were far behind expectations owing to their high threading dislocation densities (TDDs), in the 10 8 to 10 9 cm −2 range. 1,2) However, the use of native freestanding GaN substrates with low TDD values in the 10 6 cm −2 range or lower, which were developed by several groups, including ours, [3][4][5][6][7][8] made it possible to realize highperformance devices having high voltage-blocking capabilities together with low on-resistances, as expected from the wide band gap of the materials. [9][10][11][12][13] To achieve high breakdown voltages in GaN Schottky and PN diodes (PNDs), precise control of the donor concentration in the drift layers within the range of 10 16 cm −3 or lower is required.…”

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confidence: 99%

Elimination of macrostep-induced current flow nonuniformity in vertical GaN PN diode using carbon-free drift layer grown by hydride vapor phase epitaxy

Fujikura

Hayashi

Horikiri

et al. 2018

Appl. Phys. Express

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In vertical GaN PN diodes (PNDs) grown entirely by metal–organic chemical vapor deposition (MOCVD), large current nonuniformity was observed. This nonuniformity was induced by macrosteps on the GaN surface through modulation of carbon incorporation into the n-GaN crystal. It was eliminated in a hybrid PND consisting of a carbon-free n-GaN layer grown by hydride vapor phase epitaxy (HVPE) and an MOCVD-regrown p-GaN layer. The hybrid PND showed a fairly low on-resistance (2 mΩ cm2) and high breakdown voltage (2 kV) even without a field plate electrode. These results clearly indicated the strong advantages of the HVPE-grown drift layer for improving power device performance, uniformity, and yield.

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Hardness control for improvement of dislocation reduction in HVPE-grown freestanding GaN substrates

Cited by 18 publications

References 20 publications

Nanoindentation Induced Elastic-plastic Deformation of GaN Nanomembrane on a Sapphire Substrate

Nanoindentation Induced Elastic-plastic Deformation of GaN Nanomembrane on a Sapphire Substrate

Anomalous dislocation annihilation behavior observed in a GaN crystal grown on point seeds by the Na-flux method

Elimination of macrostep-induced current flow nonuniformity in vertical GaN PN diode using carbon-free drift layer grown by hydride vapor phase epitaxy

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