Growth and Characterization of Nitrogen‐Polar AlGaN/AlN Heterostructure for High‐Electron‐Mobility Transistor

Ito, Tadatoshi; Sakamoto, Ryota; Isono, Tatsuya; Yao, Yongzhao; Ishikawa, Yukari; Okada, Narihito; Tadatomo, Kazuyuki

doi:10.1002/pssb.201900589

Cited by 17 publications

(19 citation statements)

References 40 publications

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“…It provides a very useful method to obtain high-crystalline-quality N-polar AlN, which is very difficult for the in situ epitaxial growth techniques. [11][12][13][14][15][16][17][18][19][20][21][22] direction of AlN films after HTA process, showing the polarity inversion region. Reprinted from [80].…”

Section: High Temperature Annealing (Hta)mentioning

confidence: 98%

“…The polarities of AlN include Al-polarity (+c-polarity) and N-polarity (−c-polarity). Except for some special applications such as lateral polarity structure (LPS) and N-polar high electron mobility transistors (HEMTs) [21,22], N-polar AlN is not desired because of its poor crystalline quality, surface morphology, and chemical stability. Ronny Kirste et al demonstrated the surface of N-polar AlN was dominated by a typical columnar morphology, with an average width of ~500 nm and a height difference of ~100 nm [23], as shown in Figure 1.…”

Section: Polarity Control Of Aln/sapphire Templatementioning

confidence: 99%

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Recent Advances in Fabricating Wurtzite AlN Film on (0001)-Plane Sapphire Substrate

Zhang

et al. 2021

Crystals

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Ultrawide bandgap (UWBG) semiconductor materials, with bandgaps far wider than the 3.4 eV of GaN, have attracted great attention recently. As a typical representative, wurtzite aluminum nitride (AlN) material has many advantages including high electron mobility, high breakdown voltage, high piezoelectric coefficient, high thermal conductivity, high hardness, high corrosion resistance, high chemical and thermal stability, high bulk acoustic wave velocity, prominent second-order optical nonlinearity, as well as excellent UV transparency. Therefore, it has wide application prospects in next-generation power electronic devices, energy-harvesting devices, acoustic devices, optical frequency comb, light-emitting diodes, photodetectors, and laser diodes. Due to the lack of low-cost, large-size, and high-ultraviolet-transparency native AlN substrate, however, heteroepitaxial AlN film grown on sapphire substrate is usually adopted to fabricate various devices. To realize high-performance AlN-based devices, we must first know how to obtain high-crystalline-quality and controllable AlN/sapphire templates. This review systematically summarizes the recent advances in fabricating wurtzite AlN film on (0001)-plane sapphire substrate. First, we discuss the control principles of AlN polarity, which greatly affects the surface morphology and crystalline quality of AlN, as well as the electronic and optoelectronic properties of AlN-based devices. Then, we introduce how to control threading dislocations and strain. The physical thoughts of some inspirational growth techniques are discussed in detail, and the threading dislocation density (TDD) values of AlN/sapphire grown by various growth techniques are compiled. We also introduce how to achieve high thermal conductivities in AlN films, which are comparable with those in bulk AlN. Finally, we summarize the future challenge of AlN films acting as templates and semiconductors. Due to the fast development of growth techniques and equipment, as well as the superior material properties, AlN will have wider industrial applications in the future.

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Section: High Temperature Annealing (Hta)mentioning

confidence: 98%

Section: Polarity Control Of Aln/sapphire Templatementioning

confidence: 99%

Recent Advances in Fabricating Wurtzite AlN Film on (0001)-Plane Sapphire Substrate

Zhang

et al. 2021

Crystals

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“…By using a flow-rate-modulation technology with an interruption time of 4 s to grow the low temperature (LT )-GaN nucleation layer, the crystalline quality of the N-polar GaN was significantly improved [11]. The sapphire substrate with a misorientation angle of 2.0° was reported to be useful to grow the N-polar AlGaN film [12]. The growth of N-polar AlN layer with flow-modulation technology was also conducted, and the full width at half maximum (FWHM) values of 72 and 1,020 arcsec were attained for (002) and (100) XRD diffractions, respectively [13].…”

Section: Introductionmentioning

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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“…[4][5][6] The N-polar GaN/AlGaN structures are attracting interest due to the AlGaN back-barrier effect and several promising results being reported. [7][8][9][10] Higher-frequency operation requires a substrate with high resistivity and breakdown voltage. Thus, semi-insulating Fe-doped GaN substrates are frequently used.…”

Section: Introductionmentioning

confidence: 99%

“…To improve the performance of AlGaN/GaN HEMTs, an aluminum nitride (AlN) interlayer is used between AlGaN and GaN because the alloy scattering can be suppressed due to AlN/GaN structure, and the electron mobility can be improved . The N‐polar GaN/AlGaN structures are attracting interest due to the AlGaN back‐barrier effect and several promising results being reported . Higher‐frequency operation requires a substrate with high resistivity and breakdown voltage.…”

Section: Introductionmentioning

confidence: 99%

Growth of N‐Polar Aluminum Nitride on Vicinal Sapphire Substrates and Aluminum Nitride Bulk Substrates

Isono

Ito

Sakamoto

et al. 2020

Physica Status Solidi (b)

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Herein, nitrogen‐polar (N‐polar, (000‐1)) aluminum nitride (AlN) is grown on sapphire substrates with various misorientation angles through metal‐organic vapor phase epitaxy. Moreover, the effect of the sapphire substrates’ misorientation angle on the surface flatness and the crystal quality of N‐polar AlN is studied. The results demonstrate that the surface flatness of the AlN layer improves as the misorientation angle of the sapphire substrates increases. Further, the root mean square of the AlN layer significantly improves to a maximum of 1 nm, in the range of the misorientation angles between 2° and 4°, as compared with the misorientation angle of 0.2° of a conventional substrate. No deterioration in crystallinity is confirmed when an AlN layer is grown on an N‐polar AlN substrate under the same growth conditions as those for the sapphire substrates.

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Growth and Characterization of Nitrogen‐Polar AlGaN/AlN Heterostructure for High‐Electron‐Mobility Transistor

Cited by 17 publications

References 40 publications

Recent Advances in Fabricating Wurtzite AlN Film on (0001)-Plane Sapphire Substrate

Recent Advances in Fabricating Wurtzite AlN Film on (0001)-Plane Sapphire Substrate

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

Growth of N‐Polar Aluminum Nitride on Vicinal Sapphire Substrates and Aluminum Nitride Bulk Substrates

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