Thermal Atomic Layer Deposition of Polycrystalline Gallium Nitride

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Abstract

We report the successful preparation of polycrystalline gallium nitride (poly-GaN) layers by thermal atomic layer deposition (ALD) at low temperatures (375–425 °C) from trimethylgallium (TMG) and ammonia (NH3) precursors. The growth per cycle (GPC) is found to be strongly dependent on the NH3 pulse duration and the NH3 partial pressure. The pressure dependence makes the ALD atypical. We propose that the ALD involves (i) the reversible formation of the hitherto-unreported TMG:NH3 surface adduct, resulting from NH3 physisorbing on a TMG surface site and (ii) the irreversible conversion of neighboring surface adducts to Ga–NH2–Ga linkages. The pressure dependence arises from the presumed reversible nature of the adduct formation on the surface, equivalent to the known reversible nature of its formation in the gas phase in metal organic chemical vapor deposition reactions. Using in situ spectroscopic ellipsometry (SE), the GPC monitored as a function of several ALD parameters is as high as 0.1 nm/cycle at 60 s NH3 pulse and 1.3 mbar NH3 partial pressure. The changes in the growth pattern (as monitored by SE) caused by changes in the ALD parameters support the proposed growth model. Ex situ characterization reveals that the layer is carbon-free, has a polycystalline wurtzitic structure, and shows a decent conformaility over Si trenches. Tuning the ALD recipe allows us to vary the layer composition from Ga-rich to stoichiometric GaN. The Ga richness is attributed to the simultaneous TMG dissociation at the deposition temperatures. This work is the first full-scale report on low temperature thermal ALD of poly-GaN from industrial precursors, occurring via a novel chemical pathway and not requiring any radical assistance (such as plasma) as used before.
Original languageEnglish
Pages (from-to)23214-23225
Number of pages12
JournalJournal of physical chemistry C
Volume123
Issue number37
DOIs
Publication statusPublished - 6 Sep 2019

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Gallium nitride
Atomic layer deposition
gallium nitrides
atomic layer epitaxy
adducts
Spectroscopic ellipsometry
Partial pressure
pressure dependence
cycles
ellipsometry
partial pressure
Organic Chemicals
Organic chemicals
Hot Temperature
gallium nitride
Ammonia
linkages
Temperature
metalorganic chemical vapor deposition
ammonia

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@article{747e35f918164f8d89639e65f7856a9e,
title = "Thermal Atomic Layer Deposition of Polycrystalline Gallium Nitride",
abstract = "We report the successful preparation of polycrystalline gallium nitride (poly-GaN) layers by thermal atomic layer deposition (ALD) at low temperatures (375–425 °C) from trimethylgallium (TMG) and ammonia (NH3) precursors. The growth per cycle (GPC) is found to be strongly dependent on the NH3 pulse duration and the NH3 partial pressure. The pressure dependence makes the ALD atypical. We propose that the ALD involves (i) the reversible formation of the hitherto-unreported TMG:NH3 surface adduct, resulting from NH3 physisorbing on a TMG surface site and (ii) the irreversible conversion of neighboring surface adducts to Ga–NH2–Ga linkages. The pressure dependence arises from the presumed reversible nature of the adduct formation on the surface, equivalent to the known reversible nature of its formation in the gas phase in metal organic chemical vapor deposition reactions. Using in situ spectroscopic ellipsometry (SE), the GPC monitored as a function of several ALD parameters is as high as 0.1 nm/cycle at 60 s NH3 pulse and 1.3 mbar NH3 partial pressure. The changes in the growth pattern (as monitored by SE) caused by changes in the ALD parameters support the proposed growth model. Ex situ characterization reveals that the layer is carbon-free, has a polycystalline wurtzitic structure, and shows a decent conformaility over Si trenches. Tuning the ALD recipe allows us to vary the layer composition from Ga-rich to stoichiometric GaN. The Ga richness is attributed to the simultaneous TMG dissociation at the deposition temperatures. This work is the first full-scale report on low temperature thermal ALD of poly-GaN from industrial precursors, occurring via a novel chemical pathway and not requiring any radical assistance (such as plasma) as used before.",
author = "Sourish Banerjee and Aarnink, {Antonius A.I.} and Gravesteijn, {Dirk J} and Kovalgin, {Alexey Y.}",
year = "2019",
month = "9",
day = "6",
doi = "10.1021/acs.jpcc.9b05946",
language = "English",
volume = "123",
pages = "23214--23225",
journal = "Journal of physical chemistry C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "37",

}

Thermal Atomic Layer Deposition of Polycrystalline Gallium Nitride. / Banerjee, Sourish ; Aarnink, Antonius A.I.; Gravesteijn, Dirk J; Kovalgin, Alexey Y.

In: Journal of physical chemistry C, Vol. 123, No. 37, 06.09.2019, p. 23214-23225.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Thermal Atomic Layer Deposition of Polycrystalline Gallium Nitride

AU - Banerjee, Sourish

AU - Aarnink, Antonius A.I.

AU - Gravesteijn, Dirk J

AU - Kovalgin, Alexey Y.

PY - 2019/9/6

Y1 - 2019/9/6

N2 - We report the successful preparation of polycrystalline gallium nitride (poly-GaN) layers by thermal atomic layer deposition (ALD) at low temperatures (375–425 °C) from trimethylgallium (TMG) and ammonia (NH3) precursors. The growth per cycle (GPC) is found to be strongly dependent on the NH3 pulse duration and the NH3 partial pressure. The pressure dependence makes the ALD atypical. We propose that the ALD involves (i) the reversible formation of the hitherto-unreported TMG:NH3 surface adduct, resulting from NH3 physisorbing on a TMG surface site and (ii) the irreversible conversion of neighboring surface adducts to Ga–NH2–Ga linkages. The pressure dependence arises from the presumed reversible nature of the adduct formation on the surface, equivalent to the known reversible nature of its formation in the gas phase in metal organic chemical vapor deposition reactions. Using in situ spectroscopic ellipsometry (SE), the GPC monitored as a function of several ALD parameters is as high as 0.1 nm/cycle at 60 s NH3 pulse and 1.3 mbar NH3 partial pressure. The changes in the growth pattern (as monitored by SE) caused by changes in the ALD parameters support the proposed growth model. Ex situ characterization reveals that the layer is carbon-free, has a polycystalline wurtzitic structure, and shows a decent conformaility over Si trenches. Tuning the ALD recipe allows us to vary the layer composition from Ga-rich to stoichiometric GaN. The Ga richness is attributed to the simultaneous TMG dissociation at the deposition temperatures. This work is the first full-scale report on low temperature thermal ALD of poly-GaN from industrial precursors, occurring via a novel chemical pathway and not requiring any radical assistance (such as plasma) as used before.

AB - We report the successful preparation of polycrystalline gallium nitride (poly-GaN) layers by thermal atomic layer deposition (ALD) at low temperatures (375–425 °C) from trimethylgallium (TMG) and ammonia (NH3) precursors. The growth per cycle (GPC) is found to be strongly dependent on the NH3 pulse duration and the NH3 partial pressure. The pressure dependence makes the ALD atypical. We propose that the ALD involves (i) the reversible formation of the hitherto-unreported TMG:NH3 surface adduct, resulting from NH3 physisorbing on a TMG surface site and (ii) the irreversible conversion of neighboring surface adducts to Ga–NH2–Ga linkages. The pressure dependence arises from the presumed reversible nature of the adduct formation on the surface, equivalent to the known reversible nature of its formation in the gas phase in metal organic chemical vapor deposition reactions. Using in situ spectroscopic ellipsometry (SE), the GPC monitored as a function of several ALD parameters is as high as 0.1 nm/cycle at 60 s NH3 pulse and 1.3 mbar NH3 partial pressure. The changes in the growth pattern (as monitored by SE) caused by changes in the ALD parameters support the proposed growth model. Ex situ characterization reveals that the layer is carbon-free, has a polycystalline wurtzitic structure, and shows a decent conformaility over Si trenches. Tuning the ALD recipe allows us to vary the layer composition from Ga-rich to stoichiometric GaN. The Ga richness is attributed to the simultaneous TMG dissociation at the deposition temperatures. This work is the first full-scale report on low temperature thermal ALD of poly-GaN from industrial precursors, occurring via a novel chemical pathway and not requiring any radical assistance (such as plasma) as used before.

U2 - 10.1021/acs.jpcc.9b05946

DO - 10.1021/acs.jpcc.9b05946

M3 - Article

VL - 123

SP - 23214

EP - 23225

JO - Journal of physical chemistry C

JF - Journal of physical chemistry C

SN - 1932-7447

IS - 37

ER -