Fundamental chemistry and modeling of group-III nitride MOVPE

Creighton, J. R.; Wang, George T.; Coltrin, Michael E.

doi:10.1016/j.jcrysgro.2006.10.060

Cited by 56 publications

(22 citation statements)

References 34 publications

(75 reference statements)

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“…EDX and ESB analysis of the lobe and the ears showed that the former is composed mostly of Ga and the latter mostly of C. Nitrogen was not detected in these particles. Formation of such particles has also been reported during the MOCVD of GaN, 95 where their origin had been attributed to the gas-phase TMG pyrolysis at high temperatures and the agglomeration of the products.…”

Section: Results and Discussionmentioning

confidence: 73%

Composite GaN–C–Ga (“GaCN”) Layers with Tunable Refractive Index

et al. 2018

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This article describes novel composite thin films consisting of GaN, C, and Ga (termed “GaCN”, as an analogue to BCN and other carbonitrides) as a prospective material for future optical applications. This is due to their tunable refractive index that depends on the carbon content. The composites are prepared by introducing alternating pulses of trimethylgallium (TMG) and ammonia (NH3) on silicon substrates to mimic an atomic layer deposition process. Because the GaCN material is hardly reported to the best of our knowledge, a comprehensive characterization is performed to investigate into its chemical nature, primarily to determine whether or not it exists as a single-phase material. It is revealed that GaCN is a composite, consisting of phase-segregated, nanoscale clusters of wurtzitic GaN polycrystals, in addition to inclusions of carbon, nitrogen, and gallium, which are chemically bonded into several forms, but not belonging to the GaN crystals itself. By varying the deposition temperature between 400 and 600 °C and the NH3 partial pressure between 0.7 × 10–3 and 7.25 mbar, layers with a wide compositional range of Ga, C, and N are prepared. The role of carbon on the GaCN optical properties is significant: an increase of the refractive index from 2.19 at 1500 nm (for carbon-free polycrystalline GaN) to 2.46 (for GaCN) is achieved by merely 10 at. % of carbon addition. The presence of sp2-hybridized C=N clusters and carbon at the interface of the GaN polycrystals are proposed to determine their optical properties. Furthermore, the formation of the GaN polycrystals in the composite occurs through a TMG:NH3 surface-adduct assisted pathway, whereas the inclusions of carbon, nitrogen, and gallium are formed by the thermal decomposition of the chemisorbed TMG species.

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Section: Results and Discussionmentioning

confidence: 73%

Composite GaN–C–Ga (“GaCN”) Layers with Tunable Refractive Index

et al. 2018

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“…The striking changes of the growth rate (at pressure >50 mbar) may be the consequence of parasitic gas-phase reactions of the sources. In the MOCVD growth, parasitic gas-phase reactions will cause nanoparticle formation and deplete the metal organic precursor significantly, and showed nonlinear dependence of solid composition on precursor fluxes. , Moreover, high pressure has a great enhancing effect on the parasitic gas-phase reactions especially when the source is reacting with heavily oxidizing oxygen in the MOCVD growth . The consumption of metal organic precursor by parasitic gas-phase reactions will reduce the growth rate before the deposition of nanoparticle Ga 2 O 3 nuclei (with pressure higher than 100 mbar).…”

Section: Resultsmentioning

confidence: 99%

Growth Pressure Controlled Nucleation Epitaxy of Pure Phase ε- and β-Ga₂O₃ Films on Al₂O₃ via Metal–Organic Chemical Vapor Deposition

Chen

Xia

Liang

et al. 2018

Crystal Growth & Design

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Pure ε- and β-phase gallium oxide (Ga2O3) films have been successfully grown on Al2O3 (001) substrate via metal–organic chemical vapor deposition (MOCVD) at a growth temperature of 500 °C. Growth pressure controlled nucleation is the dominant controlling parameter for pure phase Ga2O3 film growth. Due to the biaxial stress induced by lattice mismatch, heteroepitaxial ε-phase Ga2O3 is grown on Al2O3 by heterogeneous nucleation at low pressure. However, film growth is dominated by spherical nuclei homogeneous nucleation at a pressure higher than 100 mbar, and β-phase Ga2O3 film is grown with a mosaic surface. The optimum pressure for the growth of pure ε-Ga2O3 films with superior crystallinity is 35 mbar, whereas the pressure window for pure β-Ga2O3 growth is between 100 mbar and 400 mbar. The growth rate of β-Ga2O3 film is much lower than ε-Ga2O3 film at high pressure. On the other hand, all Ga2O3 films have shown good optical properties with a band gap of about 4.9 eV. This fundamental research will help to understand the mechanism of MOCVD growth involving high quality and pure phase ε- and β-Ga2O3 film.

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“…It may be that the introduction of TMAl is the significant factor–it is a very reactive molecule, and commonly reacts in the gas phase with ammonia to form complex clusters. [ 25 ] We suggest that the TMAl, or perhaps monomethyl aluminum (MMAl) molecules, are acting as a getter for the gallium, and reacting with it in the gas phase before it can reach the showerhead surface. This would then explain why even a low flow of TMAl removes gallium incorporation completely in subsequent InAlN layers.…”

Section: Methodsmentioning

confidence: 99%

Avoiding Gallium Pollution in Close‐Coupled Showerhead Reactors, Alternative Process Routes

Mrad

Mazel

Feuillet

et al. 2023

Physica Status Solidi (a)

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In contrast to the previous work which solved the problem of gallium pollution using hardware modifications, herein, the changes are examined to process conditions to reduce gallium pollution in InAlN layer. Using a model of GaN decomposition followed by gallium desorption and diffusion to the showerhead, different process conditions are used to limit either the desorption or the diffusion. Reducing the GaN growth temperature gives some improvement by reducing desorption, but affects channel mobility, likely due to increased carbon incorporation. Increasing the wafer–showerhead distance also reduces the gallium pollution, this time by a factor of around 2. Finally, using AlGaN layers instead of GaN as the channel completely removes gallium pollution, even for composition as low as 5%. It is suggested that in addition to reducing desorption due to alloying, the aluminum precursor may be acting as a getter for this gallium, and so stops it getting to the showerhead. A combination of these different approaches suggests that process conditions can significantly reduce gallium pollution in close‐coupled showerhead reactors.

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Fundamental chemistry and modeling of group-III nitride MOVPE

Cited by 56 publications

References 34 publications

Composite GaN–C–Ga (“GaCN”) Layers with Tunable Refractive Index

Composite GaN–C–Ga (“GaCN”) Layers with Tunable Refractive Index

Growth Pressure Controlled Nucleation Epitaxy of Pure Phase ε- and β-Ga₂O₃ Films on Al₂O₃ via Metal–Organic Chemical Vapor Deposition

Avoiding Gallium Pollution in Close‐Coupled Showerhead Reactors, Alternative Process Routes

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Fundamental chemistry and modeling of group-III nitride MOVPE

Cited by 56 publications

References 34 publications

Composite GaN–C–Ga (“GaCN”) Layers with Tunable Refractive Index

Composite GaN–C–Ga (“GaCN”) Layers with Tunable Refractive Index

Growth Pressure Controlled Nucleation Epitaxy of Pure Phase ε- and β-Ga2O3 Films on Al2O3 via Metal–Organic Chemical Vapor Deposition

Avoiding Gallium Pollution in Close‐Coupled Showerhead Reactors, Alternative Process Routes

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Growth Pressure Controlled Nucleation Epitaxy of Pure Phase ε- and β-Ga₂O₃ Films on Al₂O₃ via Metal–Organic Chemical Vapor Deposition