NanoLund and Solid State Physics, Lund University, Box 118, SE-221 00 Lund, Sweden.
Nanotechnology. 2018 Sep 28;29(39):394001. doi: 10.1088/1361-6528/aad1d2. Epub 2018 Jul 6.
Ga InP nanowire arrays are promising for various optoelectronic applications with a tunable band-gap over a wide range. In particular, they are well suited as the top cell in tandem junction solar cell devices. So far, most Ga InP nanowires have been synthesized by the use of trimethylgallium (TMGa). However, particle assisted nanowire growth in metal organic vapor phase epitaxy is typically carried out at relatively low temperatures, where TMGa is not fully pyrolysed. In this work, we developed the growth of Ga InP nanowires using triethylgallium (TEGa) as the Ga precursor, which reduced Ga precursor consumption by about five times compared to TMGa due to the lower homogeneous pyrolysis temperature of TEGa. The versatility of TEGa is shown by synthesis of high yield Ga InP nanowire arrays, with a material composition tunable by the group III input flows, as verified by x-ray diffraction measurements and photoluminescence characterization. The growth dynamics of Ga InP nanowires was assessed by varying the input growth precursor molar fractions and growth temperature, using hydrogen-chloride as in situ etchant. We observed a complex interplay between the precursors. First, trimethylindium (TMIn) inhibits Ga incorporation into the nanowires, resulting in higher In composition in the grown nanowires than in the vapor. Second, the growth rate increases with temperature, indicating a kinetically limited growth, which from nanowire effective binary volume growth rates of InP and GaP can be attributed to the synthesis of GaP in Ga InP. We observed that phosphine has a strong effect on the nanowire growth rate with behavior expected for a unimolecular Langmuir-Hinshelwood mechanism of pyrolysis on a catalytic surface. However, growth rates increase strongly with both TEGa and TMIn precursors as well, indicating the complexity of vapor-liquid-solid growth for ternary materials. One precursor can affect the decomposition of another, and each precursor can affect the wetting properties and catalytic activity of the metal particle.
GaInP 纳米线阵列在各种光电应用中具有广阔的可调带隙，是很有前途的材料。特别是，它们非常适合作为串联结太阳能电池器件的顶电池。到目前为止，大多数 GaInP 纳米线是通过使用三甲基镓（TMGa）合成的。然而，在金属有机气相外延中，颗粒辅助纳米线生长通常在相对较低的温度下进行，在这种温度下，TMGa 没有完全热解。在这项工作中，我们使用三乙基镓（TEGa）作为 Ga 前体开发了 GaInP 纳米线的生长，由于 TEGa 的均相热解温度较低，与 TMGa 相比，Ga 前体的消耗减少了约五倍。TEGa 的多功能性通过合成高产率的 GaInP 纳米线阵列得到了证明，通过改变 III 族输入流，可以调节材料的组成，这通过 X 射线衍射测量和光致发光特性得到了验证。通过使用氯化氢作为原位蚀刻剂，改变输入生长前体的摩尔分数和生长温度，评估了 GaInP 纳米线的生长动力学。我们观察到了前体之间的复杂相互作用。首先，三甲基铟（TMIn）抑制 Ga 掺入纳米线中，导致生长的纳米线中的 In 组成高于蒸气中的 In 组成。其次，生长速率随温度升高而增加，表明生长是动力学受限的，从 GaInP 的纳米线有效二元体积生长速率来看，这归因于 GaP 在 GaInP 中的合成。我们观察到磷化氢对纳米线生长速率有很强的影响，其行为符合催化表面上热解的单分子 Langmuir-Hinshelwood 机制。然而，生长速率也随着 TEGa 和 TMIn 前体的增加而强烈增加，这表明三元材料的汽液固生长非常复杂。一种前体可以影响另一种前体的分解，而每种前体都可以影响金属颗粒的润湿性和催化活性。
