N-polar GaN evolution on nominally on-axis c-plane sapphire by MOCVD part-I: Growth optimization

Yaddanapudi, Krishna; Saha, Sabyasachi; Muraleedharan, K.; Banerjee, D.

doi:10.1016/j.mseb.2022.116038

Cited by 3 publications

(2 citation statements)

References 48 publications

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“…Nevertheless, given the limited availability and exorbitant prices of the bulk GaN substrates, it is essential to develop the GaN growth on foreign substrates. Although N-polar GaN with a smooth surface has been achieved on sapphire [24,25], SiC is preferable in terms of heat dissipation and lattice mismatch. Previous studies have demonstrated that PA-MBE-grown N-polar GaN HEMT heterostructures on SiC substrates have excellent performance [6,[26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

“…Unlike Ga-polar GaN growth [32][33][34][35], the origin of the rougher surface of Npolar GaN is not clear. Using MOCVD growth, the N-polar GaN growth evolution on on-axis sapphire [25,36,37], the effect of the AlN on the morphology [24,38], and the GaN growth conditions [39][40][41] have been widely studied. The typical PA-MBE-grown Ga-polar GaN on on-axis Si-face SiC has also been widely reported to proceed through the screwtype dislocation-mediated step-flow growth mechanism [42].…”

Section: Introductionmentioning

confidence: 99%

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Surface morphology evolution of N-polar GaN on SiC for HEMT heterostructures grown by plasma-assisted molecular beam epitaxy

Huo¹,

Lingaparthi²,

Dharmarasu³

et al. 2023

J. Phys. D: Appl. Phys.

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The surface morphology evolution of N-polar GaN with growth time was investigated and compared with Ga-polar GaN. N-polar GaN directly grown on SiC substrates was found to have slower three-dimensional (3D) to two-dimensional (2D) growth transformation and lesser coalescence than the Ga-polar counterpart, resulting in rougher surface morphology, whereas the AlN nucleation layer (NL) accelerated 3D to 2D transformation, resulting in smoother surface morphology. N-polar GaN was found to have mound-type surface morphology with clustered atomic steps, unlike the regular screw-type dislocation-mediated step-flow growth observed for Ga-polar GaN. This was explained by the lower diffusion of adatoms on the N-polar surface due to its higher surface energy and higher Ehrlich-Schwoebel barrier (ESB). In addition, the increased III/V ratio in N-polar GaN growth was found to reduce the surface roughness from 2.4 nm to 1 nm. Without Si doping, the N-polar GaN HEMT heterostructures grown under optimized conditions with smoother surface morphologies exhibited sheet carrier density of 0.91 × 1013 cm-2 and mobility of 1220 cm2/V∙s. With Si δ-doping, the sheet carrier density was increased to 1.28 × 1013 cm-2 while the mobility was reduced to 1030 cm2/V∙s. These results are comparable to the state-of-the-art data of PA-MBE-grown N-polar GaN HEMT heterostructures on SiC substrates.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Surface morphology evolution of N-polar GaN on SiC for HEMT heterostructures grown by plasma-assisted molecular beam epitaxy

Huo¹,

Lingaparthi²,

Dharmarasu³

et al. 2023

J. Phys. D: Appl. Phys.

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N-polar GaN evolution on nominally on-axis c-plane sapphire by MOCVD Part-II: Microstructural investigation

Saha¹,

Yaddanapudi²,

Channagiri³

et al. 2022

Materials Science and Engineering: B

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High-quality GaN thin film deposition at low temperature by ECR plasma-assisted sputter deposition method and its dependence of sapphire substrate misorientation angle

Torii,

Matsui

2024

Journal of Vacuum Science &Amp; Technology A

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Gallium nitride (GaN) thin films were deposited by electron cyclotron resonance (ECR) plasma-assisted sputtering, which combines GaN-magnetron sputtering with argon and nitrogen plasma assistance using an ECR high-density plasma. GaN films on the misorientation-angle-0.0° (just) sapphire substrate showed very good crystallinity with a GaN(0002) rocking curve (XRC) full width at half maximum (FWHM) of 0.042° and epitaxial growth confirmed by φ-scan measurements at a low heating temperature of 350 °C. However, the GaN thin film had a rough surface with circular grains about 100 nm in diameter and a surface root-mean-square height (Sq) of 1.21 nm. Therefore, the misorientation angle of the sapphire substrate was varied from 0.2° to 10.0°. As a result, the grains observed on the just substrate disappeared at 0.5°. The film had Sq: 0.33 nm, and the FWHM of the XRC of GaN(0002) was 0.066°, indicating improved surface flatness while maintaining crystallinity. This is considered to be due to the step flow, which promotes ECR plasma-assisted diffusion on the terrace even at the low temperature of 350 °C. The polarity of the GaN thin film was analyzed by time-of-flight atomic scattering surface analysis and found to be N-polar on all substrates.

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N-polar GaN evolution on nominally on-axis c-plane sapphire by MOCVD part-I: Growth optimization

Cited by 3 publications

References 48 publications

Surface morphology evolution of N-polar GaN on SiC for HEMT heterostructures grown by plasma-assisted molecular beam epitaxy

Surface morphology evolution of N-polar GaN on SiC for HEMT heterostructures grown by plasma-assisted molecular beam epitaxy

N-polar GaN evolution on nominally on-axis c-plane sapphire by MOCVD Part-II: Microstructural investigation

High-quality GaN thin film deposition at low temperature by ECR plasma-assisted sputter deposition method and its dependence of sapphire substrate misorientation angle

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