Organometallic precursors to the formation of GaN by MOCVD: structural characterisation of Me3Ga · NH3 by gas-phase electron diffraction

Almond, Matthew J.; Jenkins, Carolyn E.; Rice, David A.; Hagen, Kolbjørn

doi:10.1016/0022-328x(92)85091-a

Cited by 52 publications

(45 citation statements)

References 16 publications

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“…3 A primary gas phase reaction is the strong adduct forming reaction between NH 3 and TMG. [4][5][6][7] In this present study, we have directly monitored this gas phase reaction in order to better understand its impact on the growth process and system design under those conditions particularly important for MOVPE growth. The species responsible for growth are the direct result of these gas phase reactions.…”

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confidence: 99%

“…TMG and NH 3 , like other III-V Lewis acid-Lewis base combinations, 4 can form intermediate coordination compounds at low temperatures. [5][6][7]14,15 The adduct compound trimethylgalliummonamine ͑TMG:NH 3 ͒ forms between the electron acceptor ͑Lewis acid͒ TMG and the electron donor ͑Lewis base͒ ammonia, as indicated in Eq. ͑1͒:…”

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confidence: 99%

“…[5][6][7]14 It has a moderate melting point of 31°C and has a low vapor pressure of about 1 Torr at room temperature. 15 The estimated and measured strength of this Ga-N coordination bond are 21.1 kcal/mol and 18.5 kcal/ mol, respectively.…”

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High temperature adduct formation of trimethylgallium and ammonia

Thon¹,

Kuech²

1996

Applied Physics Letters

152

106

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High temperature gas phase reactions between trimethylgallium ͑TMG͒ and ammonia were studied by means of in situ mass spectroscopy in an isothermal flow tube reactor. The temperature, pressure, and reaction time were chosen to emulate the gas phase environment typical of the metal-organic vapor phase epitaxy ͑MOVPE͒ of GaN. The main gas phase species is ͓(CH 3 ͒ 2 Ga:NH 2 ͔ x , where most probably xϭ3, resulting from the very fast adduct formation followed by elimination of methane. The further gas phase decomposition of this species proceeds through the stepwise elimination of methane. These studies indicate that little TMG exists within the growth ambient under most MOVPE growth conditions. The further gas phase reaction of ͓(CH 3 ͒ 2 Ga:NH 2 ͔ x may be responsible for the strong dependence of the MOVPE GaN growth rate and uniformity commonly observed. © 1996 American Institute of Physics. ͓S0003-6951͑96͒00527-X͔The metal-organic vapor phase epitaxy ͑MOVPE͒ has emerged as the current growth technique of choice for the growth of GaN for device structures.1 Recent successes in the MOVPE formation of commercially viable blue and green light emitters have resulted in an increased activity in understanding the growth process and its relationship to the physical properties of these materials. While MOVPE can produce these materials, the growth of device-quality GaN is complicated by the severe and complicated gas phase interactions, that occur between trimethylgallium ͓͑TMG or (CH 3 ͒ 3 Ga͔ and ammonia, NH 3 which are the commonly used growth precursors.2 These gas phase interactions have been suggested to lead to gas phase depletion of the growth nutrients leading to a degradation in the growth uniformity and efficiency.3 A primary gas phase reaction is the strong adduct forming reaction between NH 3 and TMG. [4][5][6][7] In this present study, we have directly monitored this gas phase reaction in order to better understand its impact on the growth process and system design under those conditions particularly important for MOVPE growth. The species responsible for growth are the direct result of these gas phase reactions.The gas phase reactions of both TMG and NH 3 , individually, are relatively understood at this point. The pyrolysis of TMG has been widely studied. [8][9][10][11][12] The initial step in the TMG decomposition is generally agreed to be the removal of the first methyl radical, resulting in methane as the main product released in the decomposition. In the stepwise first order decomposition of TMG, an apparent activation energy has been measured for the first and second methyl groups, of 58-60 kcal/mol ͑Refs. 8 and 10͒ and 35.4 kcal/ mol, respectively.8 Under similar thermal conditions ammonia is quite stable. The gas phase decomposition of NH 3 occurs only at very high temperatures. 13 The heterogeneous decomposition of NH 3 may, therefore, be essential to GaN growth.The gas phase reaction between (CH 3 ) 3 Ga and NH 3 is less understood, particularly at elevated temperatures characteristic of MOVPE ...

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High temperature adduct formation of trimethylgallium and ammonia

Thon¹,

Kuech²

1996

Applied Physics Letters

152

106

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“…In spite of the success of MOVPE in the production of high brightness light emitting diodes 1 and short wavelength injection lasers, 2 little is known about the fundamental chemistry and transport phenomena that govern the GaN growth process. Severe gas phase pre-deposition reactions exist between the commonly employed MOVPE precursors, typically trimethylgallium (TMG) and ammonia, 3 The metalorganic vapor phase epitaxy of GaN is complicated by the extensive and pervasive complex gas phase chemistry within the growth system. This gas phase chemistry leads to the high sensitivity of the material properties on the detailed fluid dynamics within the system.…”

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Model development of GaN MOVPE growth chemistry for reactor design

Sun

Redwing²,

Kuech

2000

Journal of Elec Materi

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“…[23][24][25] Developments in computer simulation technology have allowed us to analyze the elementary reactions numerically, and several reaction models have been reported, which were capable of reproducing experimental results with specific reactor configurations and growth conditions. [26][27][28][29][30][31][32][33] Several plausible candidate growth species that contribute to layer growth have been reported, including TMGa:NH 3 adducts, [(CH 3 ) 2 GaNH 2 ] 3 , [34][35][36] diatomic GaN, 37,38 and GaNH 2 . 39 However, a model that can describe the growth behavior consistently in all reactor configurations and for all process conditions remains elusive.…”

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Kinetic Analysis of GaN-MOVPE via Thickness Profiles in the Gas Flow Direction with Systematically Varied Growth Conditions

Momose

Kamiya

Suzuki

et al. 2016

ECS J. Solid State Sci. Technol.

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We carried out a kinetic analysis of metallorganic vapor phase epitaxy (MOVPE) of GaN to investigate the dependence of the growth rate on the process conditions as a function of residence time of the precursors in the reactor. The wafer was not rotated during growth, allowing us to analyze the thickness profile of the film in the direction of gas flow, and hence the dependence of the growth rate on the residence time. The growth rate is determined mainly by the concentration of the growth species and mass transfer of the growth species to the wafer surface. The growth rate peaked in the flow direction, and the position of this peak could, in most cases, be explained by considering a combination of the linear gas velocity and the time constant for vertical diffusion of trimethylgallium (TMGa) and/or growth species across the NH 3 feed stream to the wafer surface. In some cases this was not possible, indicating that more complex effects were significant. This work is expected to contribute to understanding of the reaction pathways for GaN-MOVPE, and the growth rate data reported here are expected to provide useful benchmarks for growth simulations that combine computational fluid dynamics and reaction models. Gallium nitride (GaN) is a III/V compound semiconductor material with considerable potential for optoelectronic and high-power electronic devices due to its wide bandgap and high breakdown voltage.1-5 For these reasons, GaN is currently used for mass-produced light-emitting diodes (LEDs), lasers, and high-frequency devices. 6-10Metalorganic vapor phase epitaxy (MOVPE) is commonly employed to manufacture GaN films using trimethylgallium (TMGa) and NH 3 as group-III and group-V precursors, respectively. Research into the growth mechanisms involved in GaN-MOVPE in both academic and industrial institutions has found that the reaction chemistry is relatively complicated, consisting of gas-phase reactions followed by surface reactions. [11][12][13][14][15][16][17] This intrinsic complexity of the reactions suggests that it is not straightforward to design optimal reactors for mass production as well as settling the optimal growth conditions via conventional empirical approaches. Therefore, a variety of studies have been carried out with the aim of understanding GaN-MOVPE. Initially, attention mainly focused on identification of intermediate species that are generated from the gas-phase precursors, which contribute to the layer growth. It then became apparent that parasitic reactions in the gas phase resulted in the formation of adducts, even in the non-heated area of the reactor, in addition to those formed in the hot zone in the vicinity of the heated substrate.18,19 Some of these reaction products led to particle formation without contributing to layer growth. [20][21][22] 39 However, a model that can describe the growth behavior consistently in all reactor configurations and for all process conditions remains elusive. This is our concern, and necessitates comprehensive investigation on the behavior of GaN growt...

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Organometallic precursors to the formation of GaN by MOCVD: structural characterisation of Me3Ga · NH3 by gas-phase electron diffraction

Cited by 52 publications

References 16 publications

High temperature adduct formation of trimethylgallium and ammonia

High temperature adduct formation of trimethylgallium and ammonia

Model development of GaN MOVPE growth chemistry for reactor design

Kinetic Analysis of GaN-MOVPE via Thickness Profiles in the Gas Flow Direction with Systematically Varied Growth Conditions

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