Quantum Chemistry Study on Gas Reactions Involved with Radicals in GaN-MOVPE Process

Abstract

Abstract: The gas-phase reactions involved with radicals in the TMG/NH₃/H₂ system of MOVPE process were studied by the density functional theory (DFT) of quantum chemistry. In particular, the effects of H and NH₂radicals on the pyrolysis, hydrogenolysis and adduct paths of Ga(CH₃)₃ (denoted as TMG) were studied. By calculating of the Gibbs energies ΔG and energy barriers ΔG^*/RT of different reaction paths, the roles of radicals on the reaction paths at different temperatures were determined. The study found that when T<683 K, TMG reacts with NH₃ to generate TMG:NH₃. When T>683 K, TMG:NH₃ decomposes back into TMG and NH₃. At MOVPE condition TMG is difficult to pyrolyze directly. While with H radicals involved, TMG can be easily pyrolyzed into Ga(CH₃)₂(denoted as DMG), GaCH₃(denoted as MMG) and Ga atom. When T<800 K, the rate of amide reaction between TMG and NH₃ is greater than the rate of pyrolysis with H radicals, the reaction is dominated by amide reaction. When T>800 K, the rate of pyrolysis with H radicals is greater than the rate of amide reaction, the reaction is dominated by pyrolysis with H radicals. Since the energy barrier of hydrogenolysis is rather high, the reaction can be ignored. TMG and its pyrolysis products can react with NH₂ radicals easily to produce amide DMGNH₂. The amides can further react with H radicals and eventually generate GaNH₂ as surface reaction precursors.

Key words: GaN, MOVPE, DFT, radical, gas reaction

CLC Number:

TN304.2

LIU Guofeng, ZUO Ran. Quantum Chemistry Study on Gas Reactions Involved with Radicals in GaN-MOVPE Process[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2021, 50(3): 469-476.

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