Reduction of threading dislocation densities of N-polar face-to-face annealed sputtered AlN on sapphire

Shojiki, Kanako; Uesugi, Kenjiro; Kuboya, Shigeyuki; Miyake, Hideto

doi:10.1016/j.jcrysgro.2021.126309

Cited by 19 publications

(27 citation statements)

References 53 publications

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“…The full width at half of maximums (FWHMs) of the ( 0002) and (10 12) peaks were extracted to be 14 and 380 arcsec, respectively. These values are very close to those [10/350 arcsec for (0002)/(10 12) peak] measured on the AlN template substrates used in this study (16), suggesting high-quality homoepitaxial growth of the N-polar AlN without noticeable additional generation of structural defects (see Fig. 6E).…”

Section: Resultssupporting

confidence: 88%

“…Specifically, Al-polar AlN exhibits defect-selective etch behavior by KOH with hexagonal pits generated around dislocations (13,24). In contrast, N-polar AlN can be etched by KOH with a much higher etch rate, with hexagonal pyramids bounded by more chemically stable {1 10 1} crystallographic planes emerging after etching (13,16,25). Figure 4 shows the surface morphologies of both samples after etching in 50 wt% KOH aqueous solution at room temperature for 10 minutes.…”

Section: Resultsmentioning

confidence: 99%

“…It is very likely that surface impurities such as oxygen contribute to the polarity inversion of sample A. In fact, oxygen has been found to play an important role in the polarity inversion from N-polar to Al-polar during AlN growth by other growth techniques including MOVPE and sputtering (16,17,27). For example, the polarity of AlN grown on oxygen-plasma treated Npolar AlN surface was found to be Al-polar (27).…”

Section: Resultsmentioning

confidence: 99%

“…Details about the preparation of N-polar AlN templates can be found elsewhere (16). This costeffective growth method can produce large-area N-polar AlN templates.…”

Section: Methodsmentioning

confidence: 99%

“…The first step to achieve N-polar III-N HEMTs based on the AlN platform is the epitaxial growth of high-quality N-polar AlN. N-polar AlN has been synthesized on different foreign substrates such as Si, SiC and sapphire using techniques such as metal-organic vapor phase epitaxy (MOVPE), sputtering and molecular beam epitaxy (MBE) (11)(12)(13)(14)(15)(16)(17)(18). Among these, optimal conditions for the MOVPE growth of N-polar AlN have been developed on C-face SiC substrates with an intentional miscut of 1°to achieve a smooth surface free of hexagonal hillocks and step bunching (13).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Molecular beam homoepitaxy of N-polar AlN: enabling role of Al-assisted surface cleaning

Zhang¹,

Hayashi²,

Tohei³

et al. 2022

Preprint

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…Details about the preparation of N-polar AlN templates can be found elsewhere (16). This costeffective growth method can produce large-area N-polar AlN templates.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Molecular beam homoepitaxy of N-polar AlN: enabling role of Al-assisted surface cleaning

Zhang¹,

Hayashi²,

Tohei³

et al. 2022

Preprint

Self Cite

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Probing the Thermal and Electrical Properties of Ultrawide Bandgap Nitrogen‐Polar AlGaN Heterostructures

Noshin,

Kwon,

Khan

et al. 2024

Adv Funct Materials

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Ultra‐wide bandgap semiconductor AlGaN is a promising candidate for high‐power and high‐frequency electronics. AlGaN‐heterostructures with nitrogen (N)‐polarity can offer added benefits of low‐leakage and large drive current. However, electro‐thermal transport in such heterostructures remains unexplored, although they are essential for electronic device functionality. Here, the thermal and electrical properties of N‐polar AlxGa1‐xN‐channel heterostructures (Al percentage, x = 15–90%) are explored and compared with their GaN counterpart. The thermal measurements uncover that the effective thermal resistance of the thin channel and barrier layers are similar in magnitudes for N‐polar‐ AlGaN and GaN heterostructures, however, the total effective thermal conductivity in N‐polar AlGaN heterostructure is ≈4× smaller. This reduction originates from the larger thermal resistance of the thick Al0.15Ga0.85N buffer layer within the AlGaN stack. N‐polar AlxGa1‐xN stack displays a thermal conductivity almost independent of temperature, measured from room temperature up to 200 °C. Hall measurements of an N‐polar Al0.30Ga0.70N‐channel heterostructure further reveal that electrical properties such as resistivity, carrier density, and mobility remain nearly unchanged with temperature, indicating the dominance of alloy‐phonon scattering in such material systems. These results offer important insights into material‐device co‐design and reliability of N‐polar AlGaN heterostructures.

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Beyond Structural Stabilization of Highly‐Textured AlN Thin Films: The Role of Chemical Effects

Pshyk,

Patidar,

Alinezhadfar

et al. 2024

Adv Materials Inter

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The crystalline quality and degree of c‐axis orientation of hexagonal AlN thin films correlate directly with their functional properties. Therefore, achieving AlN thin films of high crystalline quality and texture is of extraordinary importance for many applications, but particularly in electronic devices. This systematic study reveals, that the growth of c‐axis‐orientated AlN thin films can be governed by a chemical stabilization effect in addition to the conventionally known structural, strain‐induced, stabilization mechanism. The promotion of in‐plane growth of AlN grains with c‐axis out‐of‐plane orientation is demonstrated on Y, W, or Al seed layers with different thicknesses and crystallinity preliminary exposed to N2 at room temperature. It is established that the stabilization mechanism is chemical in nature: the formation of an N‐rich surface layer on the metal seed layers upon exposure to N2 pre‐determines the polarity of AlN islands at the initial stages of thin film growth while the low energy barrier for the subsequent coalescence of islands of the same polarity contributes to grain growth. These results suggest that the growth of c‐axis oriented AlN thin films can be optimized and controlled chemically, thus opening more pathways for energy‐efficient and controllable AlN thin film growth processes.

show abstract

Reduction of threading dislocation densities of N-polar face-to-face annealed sputtered AlN on sapphire

Cited by 19 publications

References 53 publications

Molecular beam homoepitaxy of N-polar AlN: enabling role of Al-assisted surface cleaning

Molecular beam homoepitaxy of N-polar AlN: enabling role of Al-assisted surface cleaning

Probing the Thermal and Electrical Properties of Ultrawide Bandgap Nitrogen‐Polar AlGaN Heterostructures

Beyond Structural Stabilization of Highly‐Textured AlN Thin Films: The Role of Chemical Effects

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