Modeling the Non-Equilibrium Process of the Chemical Adsorption of Ammonia on GaN(0001) Reconstructed Surfaces Based on Steepest-Entropy-Ascent Quantum Thermodynamics

Materials

Michael R. von Spakovsky¹  Yoshihiro Kangawa²  Akira Kusaba²  Koichi Kakimoto²  Guanchen Li³ 

[1] Center for Energy Systems Research (CESR), Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24061, USA;Department of Aeronautics and Astronautics, Kyushu University, Fukuoka 819-0395, Japan;Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK;

关键词: metalorganic vapor phase epitaxy;    gallium nitride;    chemical adsorption;    surface reconstruction;    density functional theory calculations;    steepest-entropy-ascent quantum thermodynamics;   

DOI  :  10.3390/ma10080948

来源: DOAJ

【 摘 要 】

Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and Nad-H + Ga-H on a 2 × 2 unit cell) is investigated using steepest-entropy-ascent quantum thermodynamics (SEAQT). SEAQT is a thermodynamic-ensemble based, first-principles framework that can predict the behavior of non-equilibrium processes, even those far from equilibrium where the state evolution is a combination of reversible and irreversible dynamics. SEAQT is an ideal choice to handle this problem on a first-principles basis since the chemical adsorption process starts from a highly non-equilibrium state. A result of the analysis shows that the probability of adsorption on 3Ga-H is significantly higher than that on Nad-H + Ga-H. Additionally, the growth temperature dependence of these adsorption probabilities and the temperature increase due to the heat of reaction is determined. The non-equilibrium thermodynamic modeling applied can lead to better control of the MOVPE process through the selection of preferable reconstructed surfaces. The modeling also demonstrates the efficacy of DFT-SEAQT coupling for determining detailed non-equilibrium process characteristics with a much smaller computational burden than would be entailed with mechanics-based, microscopic-mesoscopic approaches.

【 授权许可】

Unknown