Reduction of the threading dislocation density in GaN films grown on vicinal sapphire (0001) substrates

Shen, Xu–Qiang; Matsuhata, Hirofumi; Okumura, Hajime

doi:10.1063/1.1849836

Cited by 101 publications

(98 citation statements)

References 16 publications

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“…www.pss-c.com [9], are clearly observable from the TEM image. The interesting feature is that the ITDs always terminate at macro-step positions on the surface as shown by arrows in the upper part of Fig.…”

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Dislocation behaviour in III‐nitride epitaxial films grown on vicinal sapphire (0001) substrates

Shen

Matsuhata

Okumura

2006

Phys. Status Solidi (c)

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Dislocation behaviour in AlN and GaN films grown on vicinal sapphire (0001) substrates are investigated using transmission electron microscopy. It is found that the dislocation behaviours strongly depend on the vicinal angle of the substrates. When the vicinal angle is 0.5 o , the dislocation lines propagate along the caxis and no bending of the dislocation line is found. On the other hand, dislocation bending occurs in the films grown on the 2.0 o -off substrates, which results in the great reduction of the dislocation density in the films. The dislocation loop formation and the combination of two dislocations into one are the main mechanisms for this reduction. The surface morphology (mono-layer and multilayer step formations) plays an important role in determining the different dislocation behaviours.1 Introduction III-nitride materials have attracted great attentions due to their potential applications in optical and electronic devices [1][2][3]. It is strongly required to realize high-quality epitaxial films with low dislocation density, because high-density dislocations, due to the lack of proper substrates for the epitaxial growth, greatly influence the properties of device operations. To solve this problem, many growth techniques have been proposed [4][5][6][7][8]. Among them, epitaxial lateral overgrowth (ELO) is the most successful technique, which has been applied to the commercialised optical devices such as LDs. However, the present techniques are still difficult to obtain the satisfied quality of epitaxial films for the purpose of electronics devices, because uniformly low dislocation density on the whole wafer is strictly required for the electronics device application. Furthermore, the processes of the present techniques are very complicated, such as additional patterning, re-growth and etc. We have proposed a new approach to uniformly reduce the dislocation density [9]. This technique is simply to use vicinal substrates for the epitaxial growth without any additional processes. In order to promote this technique to the practical application, understanding of the dislocation behaviours in the films grown on such vicinal substrates is necessary.In this study, we systematically investigate the dislocation behaviours in the ALN and the GaN films grown on the vicinal sapphire (0001) substrates observed by transmission electron microscopy (TEM). Both cross-sectional and plan-view observations were carried out to characterize the dislocation behaviours in the epitaxial films. Based on the observation results, the mechanism of the dislocation density reduction is discussed.

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“…Furthermore, the processes of the present techniques are very complicated, such as additional patterning, re-growth and etc. We have proposed a new approach to uniformly reduce the dislocation density [9]. This technique is simply to use vicinal substrates for the epitaxial growth without any additional processes.…”

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Dislocation behaviour in III‐nitride epitaxial films grown on vicinal sapphire (0001) substrates

Shen

Matsuhata

Okumura

2006

Phys. Status Solidi (c)

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“…18 The growth of nitride films was performed with pulsed magnetron sputtering sources in an N 2 /Ar atmosphere. The growth temperature was monitored using a calibrated pyrometer.…”

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N-polar InGaN-based LEDs fabricated on sapphire via pulsed sputtering

et al. 2017

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High-quality N-polar GaN epitaxial films with an atomically flat surface were grown on sapphire (0001) via pulsed sputtering deposition, and their structural and electrical properties were investigated. The crystalline quality of N-polar GaN improves with increasing film thickness and the full width at half maximum values of the x-ray rocking curves for 0002 and 101¯2 diffraction were 313 and 394 arcsec, respectively, at the film thickness of 6μm. Repeatable p-type doping in N-polar GaN films was achieved using Mg dopant, and their hole concentration and mobility can be controlled in the range of 8 × 1016–2 × 1018 cm−3 and 2–9 cm2V−1s−1, respectively. The activation energy of Mg in N-polar GaN based on a temperature-dependent Hall measurement was estimated to be 161 meV, which is comparable to that of the Ga-polar GaN. Based on these results, we demonstrated the fabrication of N-polar InGaN-based light emitting diodes with the long wavelength up to 609 nm.

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“…Our previous results clearly demonstrated that the surface morphology of the AlGaN/GaN heterostructure is free of micro-cracks by using vicinal substrate even the Al composition is as high as 0.4. Furthermore, the usage of the vicinal substrate can also reduce the dislocation density [8][9][10]. Therefore, it is expected that the gate leakage current in the HEMT can be suppressed by fabricating the device on the vicinal substrate.…”

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rf‐MBE growth and characterizations of AlGaN/GaN HEMTs on vicinal sapphire (0001) substrates

Shen

Sazawa

Okumura

2008

Phys. Status Solidi (c)

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We report the rf‐MBE growth and characterizations of AlGaN/GaN heterostructures and their HEMTs on vicinal sapphire (0001) substrates. Vicinal angle dependences of the property (surface morphologies and 2DEG mobility) in AlGaN/GaN heterostructures are investigated. It is found that the surface morphology and the 2DEG mobility is greatly improved by using vicinal substrates. Furthermore, the gate‐leakage current in the AlGaN/GaN‐based HEMTs, which is important for the device operation, is suppressed due to the improvement of the surface morphology and the reduction of the dislocation density in the heterostrucutes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Reduction of the threading dislocation density in GaN films grown on vicinal sapphire (0001) substrates

Cited by 101 publications

References 16 publications

Dislocation behaviour in III‐nitride epitaxial films grown on vicinal sapphire (0001) substrates

Dislocation behaviour in III‐nitride epitaxial films grown on vicinal sapphire (0001) substrates

N-polar InGaN-based LEDs fabricated on sapphire via pulsed sputtering

rf‐MBE growth and characterizations of AlGaN/GaN HEMTs on vicinal sapphire (0001) substrates

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