Nucleation and growth behavior for GaN grown on (0001) sapphire via multistep growth approach

Kobayashi, J. T.; Kobayashi, Naoki; Dapkus, P. D.

doi:10.1007/s11664-997-0004-0

Cited by 20 publications

(8 citation statements)

References 8 publications

(7 reference statements)

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“…Lateral growth of GaN may lead to a possible reduction in defect density and improved crystal quality, as occurs in MOVPE. 19,22 TEM or other techniques have not yet been used to count the defects in the two-stage samples.…”

Section: Two-stage Growthmentioning

confidence: 99%

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: Two-stage Growthmentioning

confidence: 99%

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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“…These reported transport properties are the best yet reported for GaN:Si films grown in this close-spaced showerhead MOCVD reactor geometry. 7,8 EXPERIMENTAL Gallium nitride films have been grown in a closespaced showerhead MOCVD reactor that has a sourceto-substrate spacing of 1 cm. Trimethylgallium (TMG) and ammonia (NH 3 ) were used as precursors, and hydrogen (H 2 ) was used as the carrier gas.…”

Section: Introductionmentioning

confidence: 99%

The impact of nitridation and nucleation layer process conditions on morphology and electron transport in GaN epitaxial films

Wickenden

Koleske

Henry

et al. 1999

Journal of Elec Materi

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A systematic study has been performed to determine the characteristics of an optimized nucleation layer for GaN growth on sapphire. The films were grown during GaN process development in a vertical close-spaced showerhead metalorganic chemical vapor deposition reactor. The relationship between growth process parameters and the resultant properties of low temperature GaN nucleation layers and high temperature epitaxial GaN films is detailed. In particular, we discuss the combined influence of nitridation conditions, V/III ratio, temperature and pressure on optimized nucleation layer formation required to achieve reproducible high mobility GaN epitaxy in this reactor geometry. Atomic force microscopy and transmission electron microscopy have been used to study improvements in grain size and orientation of initial epitaxial film growth as a function of varied nitridation and nucleation layer process parameters. Improvements in film morphology and structure are directly related to Hall transport measurements of silicon-doped GaN films. Reproducible growth of silicon-doped GaN films having mobilities of 550 cm 2 /Vs with electron concentrations of 3 × 10 17 cm -3 , and defect densities less than 10 8 cm -2 is reported. These represent the best reported results to date for GaN growth using a standard two-step process in this reactor geometry.

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“…After the GaAs cap layer was removed from I, both I and II were annealed at 1000°C in an oxygen ambient for 1 h. Finally, GaN ͑ϳ4 m͒ was grown by atmospheric pressure MOCVD using a multistep growth sequence. 9 Scanning electron microscopy shows that GaN on I grows with very smooth surface morphology, 7 while GaN on II grows as randomly oriented large grains ͑lateral size ϳ4 m͒. As shown in Ref.…”

Section: ͓S0003-6951͑98͒02737-5͔mentioning

confidence: 85%

Single-crystal α-GaN grown on a α-Ga2O3 template layer

Kobayashi

Choi

et al. 1998

Applied Physics Letters

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The mechanism for growth of single-crystal GaN on oxidized AlAs (AlOx) formed on a Si(111) substrate by metalorganic chemical vapor deposition has been studied. Cross-sectional transmission electron microscopy (XTEM) indicates that the grown GaN is single-crystal α-GaN in spite of the fact that the AlOx on which the GaN is grown is found to contain predominantly polycrystal γ-Al2O3. Reflection high-energy electron diffraction (RHEED) shows that oriented crystallized α-Ga2O3 is formed between AlOx and the GaAs cap layer during the oxidation process. The α-Ga2O3 acts as a growth template and results in the crystalline orientation of α-GaN on polycrystal γ-Al2O3. Further support for this template is derived from energy dispersive x-ray spectroscopy that shows the existence of Ga atoms on AlOx. Combined XTEM/RHEED analysis suggests that α-GaN is oriented in the growth direction as [0001]α-GaN∥[0001]α-Ga2O3∥[111]Si and the in-plane direction as [211¯0]α-GaN∥[11_00]α-Ga2O3∥[011_]Si, which can be understood by considering the misfit in the in-plane atomic separation at each interface.

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Nucleation and growth behavior for GaN grown on (0001) sapphire via multistep growth approach

Cited by 20 publications

References 8 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

The impact of nitridation and nucleation layer process conditions on morphology and electron transport in GaN epitaxial films

Single-crystal α-GaN grown on a α-Ga2O3 template layer

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