Transmission electron microscopy characterization of GaN layers grown by MOCVD on sapphire

Rouvière, J. L.; Arlery, M.; Niebuhr, R.; Bachem, K. H.; Briot, Olivier

doi:10.1016/s0921-5107(96)01855-7

Cited by 69 publications

(53 citation statements)

References 9 publications

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“…This variation in growth and decomposition rates for the different crystal directions and for high N/Ga ratios is quite similar to results obtained in lateral epitaxial overgrowth of GaN by MOVPE 19 and HVPE, and also TEM observations of nano pipes and pits. 14 The morphology seen here can also be explained by the ''opening up'' of threading dislocations into nano pits in the highly nitrogen-rich reactive environment. The density of pits in Fig.…”

Section: B Growth Under N-rich Conditionsmentioning

confidence: 72%

Morphology, polarity, and lateral molecular beam epitaxy growth of GaN on sapphire

Piquette¹,

Bridger²,

Bandić³

et al. 1999

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Gallium nitride was grown on sapphire ͑0001͒ substrates by radio frequency plasma assisted molecular beam epitaxy. The surface morphology was characterized during growth by reflection high energy electron diffraction, and ex situ by scanning electron microscopy ͑SEM͒, atomic force microscopy ͑AFM͒ and x-ray diffraction. It is found that surface morphological features are linked to domains of specific wurtzite crystal polarity, ͑0001͒Ga face or (0001 )N face, for Ga-rich growth. For growth on AlN buffer layers, we commonly observe films which consist of largely ͑0001͒Ga polarity material, as confirmed by selective etch tests, with a varying coverage of (0001 )N-face inversion domains threading along the growth direction. For growth near stoichiometric conditions, the growth rate of the N-face domains is slightly lower than that for the Ga-face matrix, which results in the formation of pits with inversion domains at their centers. For samples grown by first depositing GaN under N-rich conditions, followed by growth under Ga-rich conditions, a different morphology is obtained, exhibiting large hexagonal flat terraces observable by SEM and AFM. The apparent grain size of these films is increased substantially over films grown using a single step approach. The cross sectional SEM images of the two-step films show a network of voids and columns at the interface between the N-rich and the Ga-rich layers, above which micron-scale islands form and coalesce via lateral growth. Lateral growth may result in reduced defect density and improved crystal quality. The asymmetric x-ray peak (112 4) width is reduced to approximately 280 arcsec in the two-stage GaN films.

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Section: B Growth Under N-rich Conditionsmentioning

confidence: 72%

Morphology, polarity, and lateral molecular beam epitaxy growth of GaN on sapphire

Piquette¹,

Bridger²,

Bandić³

et al. 1999

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…Substrate nitridation strongly modifies its surface and has also a strong influence on the surface morphology and polarity of the subsequent nitride epilayers. Mixed-polarity films (i.e., films containing inversion domains (IDs) with a different polarity) of GaN [55] or AlN [56] are typically formed without sapphire nitridation. On the other hand, highly crystalline nitride layers with N-polarity are formed on the nitridated substrate [54,56].…”

Section: Substrate Nitridationmentioning

confidence: 99%

Lowering the density of dislocations in heteroepitaxial III-nitride layers: Effect of sapphire substrate treatment (review)

Parphenyuk¹

2016

Semicond. Phys. Quantum Electron. Optoelectron.

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Abstract. In this paper, different methods for lowering the dislocation density such as incorporation of the buffer layers, substrate patterning and nitridation, silan-ammonia treatment are reviewed and compared. Advantages and limitations of these methods as well as a specific mechanism to reduce the dislocation amount are discussed. Usually, high densities of threading dislocations within the range 10 10 …10 11 cm -2 are present in typical thin nitride films that are directly grown on sapphire substrate. Using these methods for substrate preparation, the density of dislocations can be reduced to the value 1·10 7 cm -2. An important process that enables to obtain the high-quality GaN layers with the low dislocation density is patterning the sapphire substrate. The dislocation density of these substrates depends on the pattern shape and orientation of patterned strips on cplane sapphire. Layers of GaN grown on a cone-shaped pattern have the lowest dislocation density. In addition, patterning the sapphire substrate increases the external quantum efficiency of radiative structures and reduces the mechanical stresses in the nitride layers.

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“…the IDB structure that leaves one atomic species invariant while the other switch their tetrahedral site occupation) by a (1/8)[0001 ] rigid body translation. Theoretical simulations and experimental observations have shown that { 01 10 } IDB*s are low-energy IDB defects [36,[38][39][40]. A substrate partial step is required if the chemical character of the interface is conserved on either side of the IDB; then structure a-cnid1 transforms to d-cnid7.…”

Section: Emanation Of Inversion Domain Boundariesmentioning

confidence: 99%

Interfacial steps, dislocations, and inversion domain boundaries in the GaN/AlN/Si (0001)/(111) epitaxial system

Dimitrakopulos

Sanchez

Komninou

et al. 2005

Physica Status Solidi (b)

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The role of substrate steps in the introduction of transformations of interfacial structure and inversion domain boundaries is studied for the GaN/AlN/Si (0001)/(111) epitaxial system using topological analysis and high resolution transmission electron microscopy. This epitaxial system can exhibit distinct interfacial structures at the AlN/Si interface, and transformations from one to the other can be introduced by the steps on the substrate surface. The interfacial steps can exhibit dislocation character and they may accommodate the coexistence of energetically degenerate as well as distinct interfacial structures. A substrate step is identified as a potential cause for pinhole formation. Inversion domain boundaries accommodate interfacial transformations when they emanate from the epitaxial interface and can reduce the coherency dislocation character of interfacial steps. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Transmission electron microscopy characterization of GaN layers grown by MOCVD on sapphire

Cited by 69 publications

References 9 publications

Morphology, polarity, and lateral molecular beam epitaxy growth of GaN on sapphire

Morphology, polarity, and lateral molecular beam epitaxy growth of GaN on sapphire

Lowering the density of dislocations in heteroepitaxial III-nitride layers: Effect of sapphire substrate treatment (review)

Interfacial steps, dislocations, and inversion domain boundaries in the GaN/AlN/Si (0001)/(111) epitaxial system

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