GaN-MOVPE 气相自由基反应的量子化学研究. (Chinese)

The gas-phase reactions involved with radicals in the TMG/ NH 3 / H 2 system of MOVPE process were studied by the density functional theory (DFT) of quantum chemistry. In particular, the effects of H and NH 2 radicals on the pyrolysis, hydrogenolysis and adduct paths of Ga(CH 3 )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 NH 3 to generate TMG∶NH 3 . When T >683 K, TMG∶NH 3 decomposes back into TMG and NH 3 . At MOVPE condition TMG is difficult to pyrolyze directly. While with H radicals involved, TMG can be easily pyrolyzed into Ga(CH 3 )2 (denoted as DMG), GaCH 3 (denoted as MMG) and Ga atom. When T <800 K, the rate of amide reaction between TMG and NH 3 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 NH 2 radicals easily to produce amide DMGNH 2 . The amides can further react with H radicals and eventually generate GaNH 2 as surface reaction precursors. [ABSTRACT FROM AUTHOR]

利用量子化学的密度泛函理论(DFT),对TMG/ NH 3 / H 2 体系中自由基参与的金属有机气相外延(MOVPE)反应 进行计算分析,特别针对H、NH 2 自由基对Ga(CH 3 ) 3 (简称TMG)热解路径、氢解路径以及加合路径的影响进行研究。 通过计算不同反应路径的吉布斯自由能差ΔG 和能垒ΔG∗ / RT,确定了自由基参与的气相反应在不同温度下不同的 反应路径。研究发现:当T <683 K 时,TMG 与NH 3 反应生成加合物TMG∶NH 3 。当T >683 K 时,TMG∶NH 3 重新分解为 TMG 和NH 3 。TMG 在MOVPE 温度下很难直接热解,在H 自由基作用下则易热解产生Ga(CH 3 ) 2 (简称DMG)、 GaCH 3 (简称MMG)和Ga 原子。当T <800 K 时,TMG 与NH 3 的氨基反应速率大于自由基参与的热解反应,故氨基反 应占主导;当T >800 K 时,自由基参与的TMG 热解反应速率大于氨基反应,故热解反应占主导。氢解反应由于能垒 很高,因此可忽略。TMG 及其热解产物与NH2 自由基反应很容易产生氨基物。氨基物DMGNH2 可以与H 自由基继续 反应,最终生成表面反应前体GaNH 2 。 [ABSTRACT FROM AUTHOR]

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