The adsorption behavior of adatoms on stepped GaN(0001) surfaces during metalorganic vapor phase epitaxy (MOVPE) is theoretically investigated on the basis of ab initio calculations. The calculations using vicinal surfaces consisting of single layer step edges along the [11̅00] direction reveal that the structure of step edges depends on the growth condition. The vicinal surface with H-terminated N atoms (N_ad-H+Ga-H) and that with both H-terminated N atoms and NH₂ (N_ad-H+Ga-NH₂) are found to be stabilized under the MOVPE growth condition. Furthermore, different adsorption sites and energies of Ga and N adatoms are obtained depending on the atomic configurations of step edges and terraces. The most stable adsorption site of the Ga adatom is located at the step edge irrespective of the reconstructions, but the adsorption energy for the surface with N_ad-H+Ga-NH₂ (−3.54 eV) is much lower than that with N_ad-H+Ga-H (−2.68 eV). One of the striking results of the adsorption behavior of the Ga adatom is the presence or absence of the Ehrlich–Schwoebel barrier, depending on the structure of step edges. On the basis of the calculated adsorption energies and energy barriers, the adsorption behavior at the step edges on GaN(0001) surfaces depending on the growth condition of MOVPE is successfully explained.

中文翻译：

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金属有机气相外延过程中台阶边缘对GaN（0001）表面吸附行为的影响：从头算研究

从头计算，从理论上研究了金属有机物气相外延（MOVPE）过程中，台阶状GaN（0001）表面上吸附原子的吸附行为。使用沿[11̅00]方向由单层阶梯边缘组成的相邻表面进行的计算表明，阶梯边缘的结构取决于生长条件。具有H终止的N原子的邻域表面（N _ad -H + Ga-H）和具有H终止的N原子和NH ₂的邻域表面（N _ad -H + Ga-NH ₂被发现在MOVPE生长条件下稳定。此外，根据台阶边缘和台阶的原子构型，获得了Ga和N原子的不同吸附位点和能量。Ga原子的最稳定吸附位点位于台阶边缘，与重建无关，但N _ad -H + Ga-NH ₂（-3.54 eV）的表面的吸附能远低于N _ad的表面-H + Ga-H（-2.68 eV）。Ga吸附原子的惊人结果之一是根据台阶边缘的结构，是否存在Ehrlich-Schwoebel势垒。根据计算出的吸附能和能垒，成功解释了MOVPE的生长条件对GaN（0001）表面台阶边缘处的吸附行为。