Concepts and mechanisms of dislocation density reduction in heteroepitaxial diamond

采用化学气相沉积法(CVD)在Ir/YSZ/Si衬底上生长晶片尺寸的异质外延金刚石。在合适的工艺条件下，厚度为2~3 mm的&gt；10×10 cm~(-2)的初始位错密度降至~7×10~(6)cm^~(-2)。为了将该材料成功应用于高功率电子学、量子传感或光学领域，进一步的还原是可取的。在这个项目中，我们将探索几个替代的概念，如使用不同掩模材料、几何形状的外延横向过度生长(ELO)，以及无掩模方法或最近发布的金属辅助终止(MAT)方法，以评估它们的效率和降低位错密度的潜在机制。在微波等离子体CVD工艺中，缺陷密度为~10.7 cm^-2的伪衬底在微波等离子体CVD工艺中被用来沉积掩膜、形成结构或生长衬底。除了简单但高精度的蚀坑计数方法外，表征还将包括高分辨率X射线衍射、拉曼光谱、光致发光光谱和阴极发光光谱以及透射电子显微镜。缺陷减少的样品将提供给加速器设施的合作伙伴，用于制备粒子和辐射探测器并分析其性能。

Heteroepitaxial diamond can be grown by chemical vapor deposition (CVD) on Ir/YSZ/Si in wafer size. Under appropriate process conditions, the initial dislocation density of > 10^10 cm^-2 drops to values of ~ 7×10^6 cm^-2 at thicknesses of 2 - 3 mm. For a successful application of the material in the fields of high power electronics, quantum sensing or optics a further reduction is desirable. In the present project we will explore several alternative concepts like epitaxial lateral overgrowth (ELO) using different mask materials, geometries, as well as mask-less approaches or the recently published Metal Assisted Termination (MAT) method in order to evaluate their efficiency and the underlying mechanisms of dislocation density reduction. Pseudosubstrates with defect densities of ~10^7 cm^-2 synthesized by heteroepitaxy will be applied to deposit masks, form structures or grow MAT layers before they are overgrown in a microwave plasma CVD process. Besides the simple but highly accurate etch pit counting method, characterization will include high resolution x-ray diffraction, Raman-, photoluminescence- and cathodoluminescence spectroscopy as well as transmission electron microscopy. Defect-reduced samples will be supplied to partners at accelerator facilities for the preparation of particle and radiation detectors and the analysis of their properties.