Morgan Nicholas, Dubrovskii Vladimir G, Stief Ann-Kristin, Dede Didem, Sanglé-Ferrière Marie, Rudra Alok, Piazza Valerio, Fontcuberta I Morral Anna
Laboratory of Semiconductor Materials, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Faculty of Physics, Saint Petersburg State University, Universitetskaya Embankment 13B, 199034 St. Petersburg, Russia.
Cryst Growth Des. 2023 Jun 12;23(7):5083-5092. doi: 10.1021/acs.cgd.3c00316. eCollection 2023 Jul 5.
Selective area epitaxy at the nanoscale enables fabrication of high-quality nanostructures in regular arrays with predefined geometry. Here, we investigate the growth mechanisms of GaAs nanoridges on GaAs (100) substrates in selective area trenches by metal-organic vapor-phase epitaxy (MOVPE). It is found that pre-growth annealing results in the formation of valley-like structures of GaAs with atomic terraces inside the trenches. MOVPE growth of GaAs nanoridges consists of three distinct stages. Filling the trench in the first stage exhibits a step-flow growth behavior. Once the structure grows above the mask surface, it enters the second stage of growth by forming {101} side facets as the (100) flat top facet progressively shrinks. In the third stage, the fully formed nanoridge begins to overgrow onto the mask with a significantly reduced growth rate. We develop a kinetic model that accurately describes the width-dependent evolution of the nanoridge morphology through all three stages. MOVPE growth of fully formed nanoridges takes only about 1 min, which is 60 times faster than in our set of molecular beam epitaxy (MBE) experiments reported recently, and with a more regular, triangular cross-sectional geometry defined solely by the {101} facets. In contrast to MBE, no material loss due to Ga adatom diffusion onto the mask surface is observed in MOVPE until the third stage of growth. These results are useful for the fabrication of GaAs nanoridges of different dimensions on the same substrate for various applications and can be extended to other material systems.
纳米尺度的选择性区域外延能够以预定义的几何形状在规则阵列中制造高质量的纳米结构。在此，我们通过金属有机气相外延（MOVPE）研究了在选择性区域沟槽中GaAs（100）衬底上GaAs纳米脊的生长机制。发现生长前的退火导致在沟槽内部形成具有原子台阶的GaAs谷状结构。GaAs纳米脊的MOVPE生长包括三个不同阶段。第一阶段填充沟槽呈现出台阶流生长行为。一旦结构生长到掩膜表面上方，随着（100）平面顶部面逐渐收缩，它通过形成{101}侧面进入第二阶段生长。在第三阶段，完全形成的纳米脊开始以显著降低的生长速率在掩膜上过度生长。我们开发了一个动力学模型，该模型准确描述了纳米脊形态在所有三个阶段中宽度依赖的演变。完全形成的纳米脊的MOVPE生长仅需约1分钟，这比我们最近报道的一组分子束外延（MBE）实验快60倍，并且具有仅由{101}面定义的更规则的三角形横截面几何形状。与MBE不同，在MOVPE中直到生长的第三阶段才观察到由于Ga吸附原子扩散到掩膜表面而导致的材料损失。这些结果对于在同一衬底上制造不同尺寸的GaAs纳米脊以用于各种应用是有用的，并且可以扩展到其他材料系统。
