Influence of nitridation process on characteristics of N-polar AlGaN films grown by MOCVD

Wang, Xiaolei; Zhang, Xiong; Zhang, Heng; Zhao, Jianguo; Wu, Zili; Dai, Qian; Wang, Shuchang; Hu, Guohua; Cui, Yiping

doi:10.1016/j.mssp.2017.03.025

Cited by 10 publications

(5 citation statements)

References 39 publications

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“…20 The III-polar domain on the lefthand side of Figure 5(a) has a homogeneous and sharp interface. Owing to the smaller surface diffusion length and consequently 3D growth mode in N-polar surfaces, 21 semipolar MQWs are formed on the slanted sidewalls of the V-shaped or truncated pyramids. III-and N-polar domains are separated by an IDB region of approximately 300 nm wide, with a V-shape defect located on top.…”

Section: Resultsmentioning

confidence: 99%

Polarity Control and Nanoscale Optical Characterization of AlGaN-Based Multiple-Quantum-Wells for Ultraviolet C Emitters

Jiang

Dai

et al. 2020

ACS Appl. Nano Mater.

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Optical properties of AlGaN UVC multiple-quantum-wells (MQWs) with nanoscale inverted polarity domains are strongly related to polar surfaces and nanoscale structures. In this work, the impact of pregrowth nitridation of the sapphire substrate on the polarity control of UVC MQW is highlighted, and the optical properties of III- and N-polar domains were distinguished. Nanoscale cathodoluminescence peak separation of more than 30 nm is observed in lateral-polarity-structure (LPS) UVC MQWs, which is ascribed to the potential minima induced by the local variation of QW thickness and Ga enrichment inside N-polar domains. After an AlGaN/AlN superlattice is inserted and the V/III ratio is enhanced during growth, the surface morphology of the N-polar domain is greatly improved, leading to a single-peak emission at a wavelength of 275 nm in both the III- and N-polar domains, and a 10-fold stronger peak intensity at the inversion domain boundary. Such understandings on the polar surface optimization and underlying reasons of peak separation enable rational design for efficient UVC emitters with improved performance.

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Section: Resultsmentioning

confidence: 99%

Polarity Control and Nanoscale Optical Characterization of AlGaN-Based Multiple-Quantum-Wells for Ultraviolet C Emitters

Jiang

Dai

et al. 2020

ACS Appl. Nano Mater.

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“…There are two competing routes for the gas-phase group-III nitride chemistry, namely the adduct formation pathway and the thermal decomposition pathway [25]. It was reported that the methyl radicals generated in the decomposition process of TMA needed more energy than TMG [26].…”

Section: Resultsmentioning

confidence: 99%

Achievement of polarity reversion from Al(Ga)-polar to N-polar for AlGaN film on AlN seeding layer grown by a novel flow‐modulation technology

Zhang

Fan

et al. 2021

J Mater Sci: Mater Electron

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N-polar AlGaN epi-layer was realized on AlN seeding layer grown with a novel flow-modulation method. The polarity reversion from Al(Ga)-polar to N-polar for AlGaN/AlN films was confirmed by KOH etching and subsequent observation with optical microscope as well as high-resolution X-ray diffraction (HR-XRD) measurement. In particular, the dependence of crystalline quality and defect size in the N-polar AlGaN epi-layers on the Ⅴ/Ⅲ ratio was investigated with HR-XRD and scanning electron microscopy (SEM). It was found that as the full width at half maximum (FWHM) value of the X-ray rocking curve (XRC) varied with the Ⅴ/Ⅲ ratio in a "W-shape" for the N-polar AlGaN epi-layers, and a FWHM value as small as 450 arcsec was achieved for the sample grown with a V/III ratio of 988. Moreover, it was revealed by the SEM measurement that the maximum diagonal length of hexagonal cone on the surface of the N-polar AlGaN epi-layers decreased sharply when a Ⅴ/Ⅲ ratio of 1,236 was used although the crystalline quality and the surface morphology of the N-polar AlGaN epi-layers were not improved simultaneously. The peculiar migration of the group-III atoms on the surface of the N-polar AlGaN epi-layer associated with the molar ratio of TMA/(TMA+TMG) was considered to be 2 responsible for this result.

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Section: Resultsmentioning

confidence: 99%

Achievement of Polarity Reversion From Al(Ga)-Polar to N-Polar For AlGaN Film on AlN Seeding Layer Grown By a Novel Flow-Modulation Technology

Zhang¹,

Zhang²,

Fan³

et al. 2021

Preprint

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N-polar AlGaN epi-layer was realized on AlN seeding layer grown with a novel flow-modulation method. The polarity reversion from Al(Ga)-polar to N-polar for AlGaN/AlN films was confirmed by KOH etching and subsequent observation with optical microscope as well as high-resolution X-ray diffraction (HR-XRD) measurement. In particular, the dependence of crystalline quality and defect size in the N-polar AlGaN epi-layers on the Ⅴ/Ⅲ ratio was investigated with HR-XRD and scanning electron microscopy (SEM). It was found that as the full width at half maximum (FWHM) value of the X-ray rocking curve (XRC) varied with the Ⅴ/Ⅲ ratio in a "W-shape" for the N–polar AlGaN epi-layers, and a FWHM value as small as 450 arcsec was achieved for the sample grown with a V/III ratio of 988. Moreover, it was revealed by the SEM measurement that the maximum diagonal length of hexagonal cone on the surface of the N-polar AlGaN epi-layers decreased sharply when a Ⅴ/Ⅲ ratio of 1,236 was used although the crystalline quality and the surface morphology of the N-polar AlGaN epi-layers were not improved simultaneously. The peculiar migration of the group-III atoms on the surface of the N-polar AlGaN epi-layer associated with the molar ratio of TMA/(TMA+TMG) was considered to be responsible for this result.

show abstract

Influence of nitridation process on characteristics of N-polar AlGaN films grown by MOCVD

Cited by 10 publications

References 39 publications

Polarity Control and Nanoscale Optical Characterization of AlGaN-Based Multiple-Quantum-Wells for Ultraviolet C Emitters

Polarity Control and Nanoscale Optical Characterization of AlGaN-Based Multiple-Quantum-Wells for Ultraviolet C Emitters

Achievement of polarity reversion from Al(Ga)-polar to N-polar for AlGaN film on AlN seeding layer grown by a novel flow‐modulation technology

Achievement of Polarity Reversion From Al(Ga)-Polar to N-Polar For AlGaN Film on AlN Seeding Layer Grown By a Novel Flow-Modulation Technology

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