化合物半导体材料空间微重力生长与性质研究

A series of impressive results including the realization of diffusion-limited growth of InxGa1-xSb and Bi2-xSbxTe3 and the finding of detached solidification in InAsxSb1-x, were achieved during the growth of compound semiconductor alloys performed aboard the SJ-10 recovery satellite. Based on these samples, this project aims to provide an in-depth understanding of fundamental events that are normally obscured and therefore are difficult to study quantitatively on the earth. Taking into account the suppression of buoyancy-driven convection in the crystal growth under microgravity, the solute diffusion coefficients, a key crystal growth parameter, will be extracted by fitting the mass balance equation at the solid-liquid interface. We also plan to clarify the underlying mechanism of detached growth which results in a significantly reduced defect density in the crystals, as well as find out possible ways to extend it into the terrestrial experiments. Moreover, in order to achieve a profound understanding of the growth kinetics, the dynamic evolution of the solid-liquid interface and the precise crystal growth rate will be explored by introducing striations in the grown crystals through periodic heat pulses. It is also an important topic to reveal the dependence of macroscopic physical properties on microgravity and its microscopic origins via systematic comparative studies. Our program not only provides new sights into the key issues of the crystal growth of compound semiconductor alloys, but also has great potentials to guide the future terrestrial crystal preparations.

实践十号返回式卫星搭载的化合物半导体合金生长实验已经取得了一些重要的初步结果，包括InGaSb、Bi2SbTe3体系发现纯扩散生长和InAsSb晶体实现非接触生长等。本项目将依托于上述样品，深入研究被地面重力掩盖的现象及规律。我们拟利用空间样品，屏蔽浮力对流影响，通过固-液界面质量平衡方程得到扩散系数这一晶体生长重要参量。其次，非接触生长有助于大幅降低晶体缺陷密度，本项目拟揭示非接触生长内在机理，并探索将之推广至地面实验的有效途径。另外，我们将利用周期热脉冲引入生长条纹，研究固-液界面的动态演化过程，并推算晶体生长速度的准确数值，理解晶体生长动力学过程。此外，通过系统的天地对比研究，探寻微重力对材料各种宏观物理性能的具体影响及其微观根源也是本项目的重要内容。基于本项目研究，不但有助于为化合物半导体合金生长关键科学问题提供新的研究视角，也可为地基晶体制备工艺的开发奠定基础。

利用实践十号返回式科学卫星，生长了InxGa1-xSb、InAsxSb1-x和Bi2Te3基化合物半导体合金，为深入研究微重力条件下的晶体生长规律提供了可能。由于微重力条件对浮力对流的抑制，InxGa1-xSb晶体实现了扩散生长，导致了组分的宏观均匀分布。InAsxSb1-x样品实现了非接触生长，这一生长模式大大降低了缺陷浓度并提高了材料电学性能。Bi2Te3基空间样品组分分布均匀性和微结构均有显著改善，因此热电性能及其均匀性明显优于地面样品。基于上述研究，我们对对流、溶质输运及组分分凝的相互作用有了更加深入的认识，同时理解了非接触生长的机理。此外，我们还拟合得到了晶体生长速度、热扩散系数等重要参量。另一方面，我们开展了地基InxGa1-xSb、InAsxSb1-x和Bi2Te3基合金晶体生长，并进行了系统的天地对比研究。基于生长动力学模拟，我们对固-液界面的动态演化过程有了更深入的认识。理论计算显示，类Cu-Pt有序化不但导致InAs0.5Sb0.5带隙的消失，还引起了立方-三斜结构转变。本项目研究不但有助于为化合物半导体合金生长关键科学问题提供新的研究视角，也必将为未来地基晶体制备工艺的开发奠定基础。基于本项目的研究成果，在npj Microgravity、Nanotechnology等学术期刊发表学术论文8篇，另有2篇学术论文未标注基金资助；申请6项国家发明专利，其中2项发明专利获得授权，培养博士/硕士研究生3人。