A study of GaN nucleation and coalescence in the initial growth stages on nanoscale patterned sapphire substrates <i>via</i> MOCVD

Chen, Yifan; Chen, Zhizhong; Li, Junze; Chen, Yiyong; Li, Chengcheng; Zhan, Jing; Yu, Tongjun; Kang, Xiaoning; Jiao, Fei; Li, Shunfeng; Zhang, Guoyi; Shen, Bo

doi:10.1039/c8ce01450g

Cited by 29 publications

(29 citation statements)

References 42 publications

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“…Both the values were red-shifted from the E 2 (high) wavenumber from a standard free-standing bulk GaN (567.5 cm −1 ), proving that the GaN epilayers in the reference and sample C were under tensile stress [ 26 ]. Shifts of the E 2 (high) phonon peak are related to the relaxation of residual strain; it can be calculated using the following equation [ 27 ]:

where ω γ and ω 0 represent the Raman wavenumbers of the E 2 (high) phonon peak of sample C and reference sample, respectively. A proportionality factor K γ (4.2 cm −1 GPa −1 ) originates from hexagonal GaN [ 28 ].…”

Section: Resultsmentioning

confidence: 99%

Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Kim

Lee

et al. 2021

Micromachines

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We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH3 growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH3 growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time. The photoluminescence peak positions and Raman spectra indicate that the internal tensile strain of the GaN layer is effectively relaxed without generating cracks. The LEDs embedded with an AlN buffer layer using NH3 growth interruption at 300 mA exhibited 40.9% higher light output power than that of the reference LED embedded with the AlN buffer layer without NH3 growth interruption. These high performances are attributed to an increased radiative recombination rate owing to the low defect density and strain relaxation in the GaN epilayer.

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Section: Resultsmentioning

confidence: 99%

Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Kim

Lee

et al. 2021

Micromachines

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“…The cross-sectional SEM images of GaN films on 10, 25, and 40 nm sputtered AlON/PSS templates were taken from the [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] direction, presented in Figure 5 . From the cross-sectional SEM image of the GaN film on the 10 nm sputtered AlON/PSS template, we could clearly observe that GaN could not coalesce well.…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, with the appropriate nucleation layer (NL), most GaN grows in the flat regions between cones, though the flat region is a rather small proportion of the whole substrate, no matter what the geometry of the pattern is [ 10 , 11 , 12 ]. However, some GaN would still form small GaN crystals on the cone sidewalls, which may have negative influences on GaN growth [ 13 , 14 ]. In our previous work, we confirmed that small GaN crystals would generate dislocations [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

“…In our previous work, we confirmed that small GaN crystals would generate dislocations [ 15 ]. When using metal organic chemical vapor deposition (MOCVD) to grow AlN or GaN NLs, the influences of small GaN crystals become more noteworthy [ 13 , 14 , 16 ]. Compared to MOCVD-grown AlN or GaN NLs, Li-Chuan Chang et al found that the utilization of ex situ sputtered AlN NLs could suppress GaN nucleation on cones and improve the quality of GaN films on PSSs [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

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Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

Gao

Peng

et al. 2020

Materials

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The utilization of sputtered AlN nucleation layers (NLs) and patterned sapphire substrates (PSSs) could greatly improve GaN crystal quality. However, the growth mechanism of GaN on PSSs with sputtered AlN NLs has not been thoroughly understood. In this paper, we deposited AlON by sputtering AlN with O2, and we found that the variation of thickness of sputtered AlON NLs greatly influenced GaN growth on PSSs. (1) For 10 nm thin AlON sputtering, no AlON was detected on the cone sidewalls. Still, GaN nucleated preferably in non-(0001) orientation on these sidewalls. (2) If the thickness of the sputtered AlON NL was 25 nm, AlON formed on the cone sidewalls and flat regions, and some small GaN crystals formed near the bottom of the cones. (3) If the sputtered AlON was 40 nm, the migration ability of Ga atoms would be enhanced, and GaN nucleated at the top of the cones, which have more chances to grow and generate more dislocations. Finally, the GaN growth mechanisms on PSSs with sputtered AlON NLs of different thicknesses were proposed.

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“…The role of GaN NL during annealing is to provide nucleation islands (NIs) for the GaN crystallites and to promote the lateral growth of the film. The thermal annealing process was found to have an important effect on the properties of the subsequent GaN film [5]. After the anealing of NL, the GaN NL will transform to three-dimensional (3D) NIs.…”

Section: Introductionmentioning

confidence: 99%

The Surface Morphology Evolution of GaN Nucleation Layer during Annealing and Its Influence on the Crystal Quality of GaN Films

Shang

et al. 2021

Coatings

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The surface morphology evolution of GaN nucleation layer (NL) after different annealing time has been investigated by atomic force microscope. The surface morphologies of GaN NL after different annealing time are island-like. It is observed that for 0-min annealing time sample nucleation islands (NIs) are high density and small in size which results in high dislocation density GaN films, while the samples with longer annealing time have low density and large size NIs which results in low dislocation density GaN films. The crystal structure of GaN NLs after different annealing time investigated by high-resolution X-ray diffraction indicates GaN NL is polycrystalline. During annealing, GaN nanocrystals misaligned with sapphire gradually disappear and GaN nanocrystals aligned with sapphire survive and grow up. Thus, the GaN NL surface has different NIs’ densities and sizes after different annealing time. The NL annealing time can effectively control the density and size of the NIs and further determine the GaN films crystal quality.

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A study of GaN nucleation and coalescence in the initial growth stages on nanoscale patterned sapphire substrates via MOCVD

Abstract: A study of GaN nucleation and coalescence behaviors in the initial growth stages on nanoscale patterned sapphire substrates (NPSS) is presented.

Cited by 29 publications

References 42 publications

Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

The Surface Morphology Evolution of GaN Nucleation Layer during Annealing and Its Influence on the Crystal Quality of GaN Films

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