Reduction of Threading Dislocations in GaN on Sapphire by Buffer Layer Annealing   in Low-Pressure Metalorganic Chemical Vapor Deposition

Hashimoto, Tadao; Yuri, Masaaki; Ishida, M.; Terakoshi, Yoshitami; Imafuji, Osamu; Sugino, Takashi; Itoh, Kunio

doi:10.1143/jjap.38.6605

Cited by 33 publications

(26 citation statements)

References 21 publications

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“…Hashimoto et al [12] and Moran et al [13] are shown. The short and long dashed lines are fits 4 n 1/2 , respectively.…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 90%

“…Reports by Hashimoto et al [12] and Moran et al [13] demonstrate that lower nuclei density should decrease the dislocation density. This data is shown in Fig.…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 93%

“…Dislocation reduction can be achieved by reducing the number of GaN nuclei that initially form on the sapphire surface [12,13]. Reports by Hashimoto et al [12] and Moran et al [13] demonstrate that lower nuclei density should decrease the dislocation density.…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 99%

“…These fits suggest that dislocation density and nucleation density are correlated. (One data point from Hashimoto et al [12] at the highest nucleation density and highest dislocation density is excluded from the fit because closer examination of the AFM images in Ref. [12] shows that the GaN nuclei are partly coalesced, resulting in an underestimation of the nucleation density.)…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 99%

“…(One data point from Hashimoto et al [12] at the highest nucleation density and highest dislocation density is excluded from the fit because closer examination of the AFM images in Ref. [12] shows that the GaN nuclei are partly coalesced, resulting in an underestimation of the nucleation density.) The difference in the prefactors (2.9x10 5 vs. 6.5x10 4 ) is due to the different substrates (sapphire vs. SiC) and growth pressures (150 torr vs. 760 torr) used for these growths.…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 99%

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Nanostructural engineering of nitride nucleation layers for GaN substrate dislocation reduction.

Koleske¹,

Lee²,

Lemp³

et al. 2009

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With no lattice matched substrate available, sapphire continues as the substrate of choice for GaN growth, because of its reasonable cost and the extensive prior experience using it as a substrate for GaN. Surprisingly, the high dislocation density does not appear to limit UV and blue LED light intensity. However, dislocations may limit green LED light intensity and LED lifetime, especially as LEDs are pushed to higher current density for high end solid state lighting sources. To improve the performance for these higher current density LEDs, simple growthenabled reductions in dislocation density would be highly prized.GaN nucleation layers (NLs) are not commonly thought of as an application of nano-structural engineering; yet, these layers evolve during the growth process to produce self-assembled, nanometer-scale structures. Continued growth on these nuclei ultimately leads to a fully coalesced film, and we show in this research program that their initial density is correlated to the GaN dislocation density.In this 18 month program, we developed MOCVD growth methods to reduce GaN dislocation densities on sapphire from 5x10 8 cm -2 using our standard delay recovery growth technique to 1x10 8 cm -2 using an ultra-low nucleation density technique. For this research, we firmly established a correlation between the GaN nucleation thickness, the resulting nucleation density after annealing, and dislocation density of full GaN films grown on these nucleation layers. We developed methods to reduce the nuclei density while still maintaining the ability to fully coalesce the GaN films. Ways were sought to improve the GaN nuclei orientation by improving the sapphire surface smoothness by annealing prior to the NL growth. Methods to eliminate the formation of additional nuclei once the majority of GaN nuclei were developed using a silicon nitride treatment prior to the deposition of the nucleation layer. Nucleation layer thickness was determined using optical reflectance and the nucleation density was determined using atomic force microscopy (AFM) and Nomarski microscopy. Dislocation density was measured using Xray diffraction and AFM after coating the surface with silicon nitride to delineate all dislocation types. The program milestone of producing GaN films with dislocation densities of 1x10 8 cm -2 was met by silicon nitride treatment of annealed sapphire followed by the multiple deposition of a low density of GaN nuclei followed by high temperature GaN growth. Details of this growth process and the underlying science are presented in this final report along with problems encountered in this research and recommendations for future work.

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“…Hashimoto et al [12] and Moran et al [13] are shown. The short and long dashed lines are fits 4 n 1/2 , respectively.…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 90%

“…Reports by Hashimoto et al [12] and Moran et al [13] demonstrate that lower nuclei density should decrease the dislocation density. This data is shown in Fig.…”

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 93%

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 99%

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 99%

Section: Correlation Between Nucleation and Dislocation Densitymentioning

confidence: 99%

See 3 more Smart Citations

Nanostructural engineering of nitride nucleation layers for GaN substrate dislocation reduction.

Koleske¹,

Lee²,

Lemp³

et al. 2009

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show abstract

Growth and Growth Methods for Nitride Semiconductors

Morkoç̌

2008

Handbook of Nitride Semiconductors and Devices

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Classic and novel methods of dislocation reduction in heteroepitaxial nitride layers

Jasiński

2005

phys. stat. sol. (c)

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Due to the lack of commercially available large size native substrates, reduction of threading dislocations remains one of the main challenges of group III-nitride based technology. This paper reviews major methods aimed at producing high-quality heteroepitaxial nitride films with reduced densities of dislocations. Methods such as, incorporation of buffer layers, substrate nitridation, interlayer insertion, silaneammonia treatment, lateral overgrowth and growth of thick nitride layers are reviewed. Advantages and drawbacks of these methods are discussed and compared.Introduction One of the main problems of the group III nitride-based technology is the lack of commercially available large-size native substrates. Sapphire or 6H-SiC substrates, are typically chosen for most nitride-based applications. These substrates however, are poorly matched to nitride films. There is, for example, a lattice mismatch of 16 and 13 % between c-plane sapphire substrates and GaN and AlN layers, respectively. As a result, the growth of nitride films directly on such substrates leads to the formation of three-dimensional (3D) islands [1,2]. In the initial stage of the growth, these slightly twisted/tilted islands coalesce leading to the formation of threading dislocations. Also, threading dislocations are formed to reduce the biaxial compressive strains [3,4] resulting from the lattice mismatch during the growth, as well as from the mismatch in thermal expansion coefficient between the layer and the substrate during the post-growth cooling. As a consequence high densities of threading dislocations, usually in the range of 10

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Reduction of Threading Dislocations in GaN on Sapphire by Buffer Layer Annealing in Low-Pressure Metalorganic Chemical Vapor Deposition

Cited by 33 publications

References 21 publications

Nanostructural engineering of nitride nucleation layers for GaN substrate dislocation reduction.

Nanostructural engineering of nitride nucleation layers for GaN substrate dislocation reduction.

Growth and Growth Methods for Nitride Semiconductors

Classic and novel methods of dislocation reduction in heteroepitaxial nitride layers

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