Mass transport and kinetic limitations in MOCVD selective-area growth

Coltrin, Michael E.; Mitchell, Christine C.

doi:10.1016/s0022-0248(03)01165-5

Cited by 67 publications

(66 citation statements)

References 35 publications

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“…By the virtue of the symmetry, we adopted a zero-flux boundary condition for the horizontal direction, i.e., at x = 0 and x = 5 in the model area, we assumed that the flux was zero. On the surface of the facets (gas-solid interfaces), the concentration of the reactant species was determined by the first order reaction rate i.e., the co-efficient between the flux and the concentration on the surface [5], which are denoted as k C , k F and k M on the (0001), (1-101) facets and the mask region, respectively. The different growth rates on the facets are represented by the different reaction rate along with the different diffusive fluxes.…”

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confidence: 99%

The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPE

Narita

Honda

Yamaguchi

et al. 2007

Phys. Status Solidi (c)

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The diffusion of Ga species in gas phase as well as on the surface are studied in selective area growth of AlGaN in low pressure metalorganic vapor phase epitaxy. The experiments were performed on a trapezoidal stripe with (0001) facet on the top and (1-101) facet on the sides. It was found that the ridge growth on the facets were sensitive to the growth pressure, in agreement with numerical results. At a low pressure of 100 Torr, we got a uniform thickness of AlGaN alloy, but the alloy composition was not uniform. Exponential variation of the composition gave the effective diffusion length of Ga on the order of 0.7 µm which was independent of the growth pressure.1 Introduction The selective area growth (SAG) of compound semiconductors has been adopted to fabricate an as grown cavity structure in a laser diode. To realize this, the control of the hetero-epitaxy on a nano-meter facet structure (nano-hetero-epitaxy) is the issue. In case of molecular beam epitaxy (MBE) on a mesa structure, the local growth behavior is governed by the surface diffusion of the source materials [1]. On the other hand, in the SAG of metalorganic vapor phase epitaxy (MOVPE), the growth behavior is determined by the diffusive transport of chemical species in the gas phase as well as on the sample surface [2]. Recently, the present authors investigated the non-uniform thickness and composition of an AlGaN alloy film in the atmospheric pressure SAG-MOVPE, and determined the apparent surface diffusion length of the order of 0.3-0.8 µm [3,4]. In those studies, however, the contribution of the diffusion phenomenon in the gas was not identified from that on the surface. The former will be weakened if the diffusion length in the gas phase is long enough. This will be realized by increasing the temperature and/or decreasing the ambient gas pressure. In this paper, we will study the effect of the ambient pressure on the apparent diffusion length in the MOVPE.

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confidence: 99%

The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPE

Narita

Honda

Yamaguchi

et al. 2007

Phys. Status Solidi (c)

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“…Even in the case when the lateral size of the mask is smaller than the diffusion length D/k for precursors in the gas phase, the growth enhancement is expected in the SAG region due to formation of an excessive precursor concentration above the masked area. In the case of GaN growth, D/k is about 11 microns [19], which is comparable to the total size of the oxide mask [ Fig. 1(a)].…”

Section: Methodsmentioning

confidence: 94%

Selective growth of GaN nanodots and nanostripes on 6H‐SiC substrates by metal organic vapor phase epitaxy

Goh

Martin

Ould-Saad

et al. 2009

Phys. Status Solidi (c)

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GaN nanodots and nanostripes with smooth sidewall surfaces have been selectively grown on 6H‐SiC substrates by metal organic vapor phase epitaxy. By varying the growth reactor pressure, we have been able to grow either isolated nanostructures or laterally overgrown structures. As confirmed by the Raman scattering and X‐ray diffraction techniques, the nanostructures have no influence of step bunching that occurs in the unmasked area of the continuous GaN film. The frequency shift of the E2 optical phonons shows that the residual strain in the nanostripes is relaxed compared to the continuous GaN film. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…2(a) and 2(b), which bends the dislocations parallel to the surface as the GaN nuclei laterally coalesce [8]. The facet formation growth conditions have been studied extensively by Coltrin et al [9,10] 3 reach them compared to the larger partially coalesced grains. Later in the growth as the lateral coalescence proceeds, the larger GaN grains must overgrow these smaller grains.…”

Section: Gan Nucleation and Initial Stages Of Growthmentioning

confidence: 99%

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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Mass transport and kinetic limitations in MOCVD selective-area growth

Cited by 67 publications

References 35 publications

The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPE

The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPE

Selective growth of GaN nanodots and nanostripes on 6H‐SiC substrates by metal organic vapor phase epitaxy

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

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