Three-dimensional imaging of threading dislocations in GaN crystals using two-photon excitation photoluminescence

Tanikawa, Tomoyuki; Ohnishi, Kazuki; Kanoh, Masaya; Mukai, Takashi; Matsuoka, Takashi

doi:10.7567/apex.11.031004

Cited by 81 publications

(72 citation statements)

References 33 publications

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“…In contrast, only Na-Ga intermetallic compounds were formed at higher temperature and lower pressure. By slowly increasing the growth temperature, a colourless transparent prismatic single crystal with a dimension of 1.0 × 0.5 × 0.5 mm 3 was obtained under 3 MPa of N 2 . This may imply that the GaN crystal is almost free from the N-deficiency.…”

Section: Progress Of Growing Bulk Gan Crystals By Na-flux Methodsmentioning

confidence: 99%

“…1,2 The main reason to this issue is related to the large mismatch of lattice structure between sapphire and GaN materials, that results in high threading dislocations. 3 If such dislocations propagate into multi-quantum wells (MQWs) active region of the LEDs, they would act as non-radiative recombination centres. The centres will significantly reduce the number of electrons and holes to recombine radiatively, thereby impairing the efficiency of the LEDs.…”

Section: Introductionmentioning

confidence: 99%

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Growth of Bulk Gallium Nitride Single Crystal by Sodium Flux Method: A Brief Review

Sin¹,

Ibrahim²,

Zainal³

2019

JPS

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Growing interest in homoepitaxial growth of nitride-based devices has driven considerable efforts towards producing bulk gallium nitride single crystal as a substrate for the devices. Therefore, the process of producing the bulk gallium nitride crystal substrate should be simple and yet cost-effective to reduce the production cost of the devices. To date, several methods of growing bulk gallium nitride crystal have been proposed. Sodium flux method is one of the most promising ways since it requires a moderate growth temperature and growth pressure, as well as being simple and costeffective. This paper will briefly review the progress made to advance the growth of bulk gallium nitride single crystal by sodium flux method, including discussing challenges and proposing possible improvements in future.

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Section: Progress Of Growing Bulk Gan Crystals By Na-flux Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Growth of Bulk Gallium Nitride Single Crystal by Sodium Flux Method: A Brief Review

Sin¹,

Ibrahim²,

Zainal³

2019

JPS

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“…Direct observation of the 3D motion of dislocation propagation will provide an important insight to control the quality of diamond. Recently, a nondestructive technique to characterize TDs using two‐photon‐excited photoluminescence (2PPL) has been demonstrated for 4H‐SiC and GaN crystals . By analyzing the band‐edge‐excited photoluminescence caused by 2PPL using a long‐wavelength laser (photon energy smaller than the band gap of materials), spatially resolved “dark spots” derived from carrier recombination near dislocations could be captured.…”

Section: D Imaging Of Dislocation Propagation By Two‐photon‐excited mentioning

confidence: 99%

Toward High‐Performance Diamond Electronics: Control and Annihilation of Dislocation Propagation by Metal‐Assisted Termination

Ohmagari

Yamada

Tsubouchi

et al. 2019

Physica Status Solidi (a)

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A major obstacle limiting diamond electronics is dislocations, which deteriorate device properties. As threading dislocations (TDs) are normally inherited from the substrate to the epitaxial layer, control and annihilation of their propagation are important. Herein, metal-assisted termination (MAT), in which the propagation of dislocations is suppressed by in situ metal doping, is proposed. Heavy W doping is realized by a hot-filament (HF) chemical vapor deposition (CVD) using heated wires at a high temperature of >2400-K. A large reduction of TD density is confirmed by cathodoluminescence studies and etch-pit analysis. The impact of dislocation reduction is investigated electrically. After insertion of the MAT buffer layer, Schottky barrier diodes (SBDs) show improved rectifying action and highly uniform characteristics even when substrates with high dislocation densities (mosaic and heteroepitaxial wafers) are used. The 3D structure of dislocation propagation is successfully captured by two-photon-excited photoluminescence (2PPL) imaging of Band-A luminescence. The 2PPL Band-A luminescence (without band-edge excitation) shows high spatial resolution in the depth direction. An abrupt decrease in TD density is captured for heteroepitaxial substrates with an inserted MAT buffer layer. The MAT technique provides an effective approach to realize high-performance diamond electronics.

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“…The TDs in the GaN epitaxial layer are often propagated from the substrate; therefore, the TDs in the GaN substrate have to be identified and analyzed. Tanikawa et al., for example, reported observation of the 3D propagation behaviors of TDs in a GaN crystal by using the MPPL method . In a normal PL measurement, excitation is performed using light with energy higher than the bandgap, and thus only information near the sample surface can be obtained.…”

Section: Introductionmentioning

confidence: 99%

Behavior of Threading Dislocations from GaN Substrate to Epitaxial Layer

Inotsume

Kokubo

Yamada

et al. 2020

Physica Status Solidi (b)

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Threading dislocations (TDs) in the GaN substrate and homoepitaxial layer are nondestructively evaluated using X‐ray topography (XRT), Raman spectroscopy, and multiphoton photoluminescence (MPPL) imaging. When the XRT and Raman mapping images are compared, TDs in the GaN substrate are identified as threading edge dislocations (TEDs), threading mixed dislocations (TMDs), and threading screw dislocations (TSDs). TDs are observed to propagate from the GaN substrate to the epitaxial layer. From MPPL imaging, the TEDs are found to be inclined in the [1true1¯00] direction, which is at 90° from the Burgers vector. The TMD studied in detail is found to be inclined in the [true1¯2true1¯0] direction, which is parallel to the Burgers vector. The feasibility of identifying TDs via analysis of the inclined direction of the dislocations in the GaN epitaxial layer is suggested.

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Three-dimensional imaging of threading dislocations in GaN crystals using two-photon excitation photoluminescence

Cited by 81 publications

References 33 publications

Growth of Bulk Gallium Nitride Single Crystal by Sodium Flux Method: A Brief Review

Growth of Bulk Gallium Nitride Single Crystal by Sodium Flux Method: A Brief Review

Toward High‐Performance Diamond Electronics: Control and Annihilation of Dislocation Propagation by Metal‐Assisted Termination

Behavior of Threading Dislocations from GaN Substrate to Epitaxial Layer

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