Deep-level defects related to the emissive pits in thick InGaN films on GaN template and bulk substrates

Sumiya, Masatomo; Toyomitsu, Naoki; Nakano, Yoshitaka; Wang, Yunlong; Harada, Y.; Sang, Liwen; Sekiguchi, Takashi; Yamaguchi, Tomohiro; Honda, Toshio

doi:10.1063/1.4974935

Cited by 16 publications

(12 citation statements)

References 23 publications

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“…The surface roughness ( R ms ), measured by atomic force microscopy, was 0.61 nm, and the full width at half maximum value of

ω (10 \bar{1} 4)

from X‐ray diffraction was 126 arcsec for the InGaN film fully strained with the GaN substrate. In addition, the defect density was confirmed to decrease by two orders of magnitude, compared with that of the sapphire substrate .…”

Section: Resultsmentioning

confidence: 87%

Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Sumiya

Honda

Sang

et al. 2015

Physica Status Solidi (a)

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We simulated III-V nitride heterojunction solar cells with a Mg-doped GaN/intrinsic InGaN/Si-doped GaN structure. We investigated the threshold dislocation density, the carrier lifetime, and the strain in the InGaN active layer. The conversion efficiency was sensitive to carrier lifetime limited by Shockely-Read recombination rather than the dislocation density. The electric field induced by the piezoelectric effect in the InGaN layer on þc polarity GaN was opposite to that in the depletion region. The recombination of photo-generated carriers in the p-GaN/i-InGaN/ n-GaN solar cell structure took place dominantly at the i/n interface even at 0 V, and the performance was remarkably degraded. It was found that this negative influence of the piezoelectric effect was reduced by a heavy doping of more than 3 Â 10 19 cm À3 into the n þ -GaN layer at the interface.

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“…The surface roughness ( R ms ), measured by atomic force microscopy, was 0.61 nm, and the full width at half maximum value of

ω (10 \bar{1} 4)

Section: Resultsmentioning

confidence: 87%

Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Sumiya

Honda

Sang

et al. 2015

Physica Status Solidi (a)

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“…However, these devices are generally constructed on foreign substrates, such as SiC, Si, and patterned sapphire substrates (PSSs). For short-wavelength laser diodes and for high-power and high-frequency devices, native GaN substrates have many advantages, such as their low level of current leakage and long lifetimes due to the high quality of the active epitaxial layer, accompanied by low dislocation densities and a lower level of lattice distortion, derived from homo-epitaxy (Liu et al, 2017 ; Sumiya et al, 2017 ; Han et al, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

Fabrication of 2-Inch Free-Standing GaN Substrate on Sapphire With a Combined Buffer Layer by HVPE

et al. 2021

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Free-standing GaN substrates are urgently needed to fabricate high-power GaN-based devices. In this study, 2-inch free-standing GaN substrates with a thickness of ~250 μm were successfully fabricated on double-polished sapphire substrates, by taking advantage of a combined buffer layer using hydride vapor phase epitaxy (HVPE) and the laser lift-off technique. Such combined buffer layer intentionally introduced a thin AlN layer, using a mix of physical and chemical vapor deposition at a relatively low temperature, a 3-dimensional GaN interlayer grown under excess ambient H2, and a coalescent GaN layer. It was found that the cracks in the epitaxial GaN layer could be effectively suppressed due to the large size and orderly orientation of the AlN nucleus caused by pre-annealing treatment. With the addition of a 3D GaN interlayer, the crystal quality of the GaN epitaxial films was further improved. The 250-μm thick GaN film showed an improved crystalline quality. The full width at half-maximums for GaN (002) and GaN (102), respectively dropped from 245 and 412 to 123 and 151 arcsec, relative to those without the 3D GaN interlayer. The underlying mechanisms for the improvement of crystal quality were assessed. This method may provide a practical route for fabricating free-standing GaN substrates at low cost with HVPE.

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“…Several PDS peaks are detected, which are marked with vertical lines at the defect levels in Fig.3(b). Referring to the spectra of GaN bulk and In x Ga 1−x N films evaluated via SSPC,10,26) the origins of T A1-T A5 can be identified as a threading dislocation 27) (T A1, as discussed later); a Ga vacancy, V Ga (T A2); a V Ga -carbon complex substitutionally incorporated into a N site, C N (T A3);28) the pit of a screw-type dislocation (TA4);26) and the charge state transition of C N (+=0; T A5) 29). In addition, each defect level of GaN can be theoretically explained simply from the V Ga charge states for up to four electrons from −3 to 1+; the (2−=3−) transition level of V Ga occurs at 2.80 eV above the VBM, followed by the (−=2−) level at 2.33 eV, the (0=−) level at 1.68 eV, and finally the (+=0) level at 0.97 eV 30).…”

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confidence: 99%

Valence band edge tail states and band gap defect levels of GaN bulk and In_xGa₁₋_xN films detected by hard X-ray photoemission and photothermal deflection spectroscopy

Sumiya

Ueda

Fukuda

et al. 2018

Appl. Phys. Express

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Tail states near the valence band maximum (VBM) and in-gap states of GaN bulk and InxGa1−xN films are observed by hard X-ray photoemission spectroscopy, and the fine structures of these defect states are characterized by photothermal deflection spectroscopy. The defects are enhanced with increasing InN mole fraction, indicating that they originate in cation-related defects and their complexes. The structural disorder, defined as the inverse of the slope of the VBM, becomes larger. Taking the semiconductor properties into account, we consider that the tail state defects are strongly localized, which implies that a mobility edge may exist for GaN and InxGa1−xN.

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Deep-level defects related to the emissive pits in thick InGaN films on GaN template and bulk substrates

Cited by 16 publications

References 23 publications

Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Fabrication of 2-Inch Free-Standing GaN Substrate on Sapphire With a Combined Buffer Layer by HVPE

Valence band edge tail states and band gap defect levels of GaN bulk and In_xGa₁₋_xN films detected by hard X-ray photoemission and photothermal deflection spectroscopy

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Deep-level defects related to the emissive pits in thick InGaN films on GaN template and bulk substrates

Cited by 16 publications

References 23 publications

Improvement of strained InGaN solar cell performance with a heavily doped n+‐GaN substrate

Improvement of strained InGaN solar cell performance with a heavily doped n+‐GaN substrate

Fabrication of 2-Inch Free-Standing GaN Substrate on Sapphire With a Combined Buffer Layer by HVPE

Valence band edge tail states and band gap defect levels of GaN bulk and InxGa1−xN films detected by hard X-ray photoemission and photothermal deflection spectroscopy

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Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Valence band edge tail states and band gap defect levels of GaN bulk and In_xGa₁₋_xN films detected by hard X-ray photoemission and photothermal deflection spectroscopy