Modeling the non-equilibrium process of the chemical adsorption of ammonia on GaN(0001) reconstructed surfaces based on steepest-entropy-ascent quantum thermodynamics

Akira Kusaba, Guanchen Li, Michael R. von Spakovsky, Yoshihiro Kangawa, Koichi Kakimoto

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number948
JournalMaterials
Volume10
Issue number8
DOIs
Publication statusPublished - Aug 15 2017

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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