Abstract Selective area growth of GaN rods by metalorganic vapor phase epitaxy has attracted great interest due to its novel applications in optoelectronic and photonics. In this work, we will present the dependence of GaN rod morphology on various growth parameters i.e. growth temperature, H 2 /N 2 carrier gas concentration, V/III ratio, total carrier gas flow and reactor pressure. It is found that higher growth temperature helps to increase the aspect ratio of the rods, but reduces the height homogeneity. Furthermore, H 2 /N 2 carrier gas concentration is found to be a critical factor to obtain vertical rod growth. Pure nitrogen carrier gas leads to irregular growth of GaN structure, while an increase of hydrogen carrier gas results in vertical GaN rod growth. Higher hydrogen carrier gas concentration also reduces the diameter and enhances the aspect of the GaN rods. Besides, increase of V/III ratio causes reduction of the aspect ratio of N-polar GaN rods, which could be explained by the relatively lower growth rate on (000-1) N-polar top surface when supplying more ammonia. In addition, an increase of the total carrier gas flow leads to a decrease in the diameter and the average volume of GaN rods. These phenomena are tentatively explained by the change of partial pressure of the source materials and boundary layer thickness in the reactor. Finally, it is shown that the average volume of the N-polar GaN rods keeps a similar value for a reactor pressure P R of 66 and 125 mbar , while an incomplete filling of the pattern opening is observed with P R of 250 mbar. Room temperature photoluminescence spectrum of the rods is also briefly discussed.

中文翻译：

---

MOVPE 选择性区域生长过程中 N 极性 GaN 棒形貌对生长参数的依赖性

摘要 通过金属有机气相外延法选择性区域生长 GaN 棒因其在光电和光子学中的新应用而引起了极大的兴趣。在这项工作中，我们将介绍 GaN 棒形态对各种生长参数的依赖性，即生长温度、H 2 /N 2 载气浓度、V/III 比、总载气流量和反应器压力。发现较高的生长温度有助于增加棒的纵横比，但降低了高度均匀性。此外，发现H 2 /N 2 载气浓度是获得垂直棒生长的关键因素。纯氮气载气导致GaN结构不规则生长，而氢气载气增加导致GaN棒垂直生长。更高的氢载气浓度也减小了直径并增强了 GaN 棒的外观。此外，V/III 比的增加导致 N 极性 GaN 棒的纵横比降低，这可以解释为当供应更多氨时，（000-1）N 极性顶面的生长速率相对较低。此外，总载气流量的增加导致 GaN 棒的直径和平均体积的减小。这些现象初步解释为反应器中原料分压和边界层厚度的变化。最后，表明 N 极性 GaN 棒的平均体积在反应堆压力 PR 为 66 和 125 mbar 时保持相似的值，而在 PR 为 250 mbar 时观察到图案开口的不完全填充。