Basic electronic and optoelectronic properties of threading dislocations in heteroepitaxial diamond

该计划旨在全面研究金刚石中位错的内在电子和光电性质。根据半导体材料的一般经验，高位错密度会使器件的性能急剧恶化。因此，人们对它们进行了深入的研究，并努力将其密度降至最低。尽管人们积极地开发金刚石电子器件，位错也被认为是金刚石的主要结构缺陷，但人们对其基本性质的认识却相当贫乏。这主要是由于缺乏明确定义的样本。本申请人的小组已经开发了一种异质外延技术，该技术最近促进了直径为~90 mm的单晶金刚石盘的合成。他们的方法有可能消除器件开发中的主要障碍，即无法获得晶片尺寸的衬底。此外，该方法现在能够控制制备包含位错的晶体，所述位错具有限定的传播方向和密度，所述密度变化超过系统研究所需的4个数量级。 计划中的工作将首先通过UV/维斯和IR吸收、光致发光（PL）和阴极发光（CL）对具有定义位错密度和线矢量的样品进行全面的光谱表征。接下来，光谱分辨光电导（SPC）和热刺激电流（TSC）的设置将被构建。随后的测量将识别和量化电活性缺陷水平。在几个合作的框架中，将进行电荷收集效率（CCE）和电荷瞬态光谱（QTS）测量，以分别获得电子和空穴的密度、捕获截面和陷阱深度。接下来，扩散系数和载流子的寿命将通过两种泵浦-探测技术来确定。最后，该材料将用于生产设备（探测器，电子设备）。除了深入了解位错的固有电子特性外，还将推导出不同应用中位错密度的临界阈值，这可以为器件开发提供基准。

The proposal aims at a comprehensive study of the intrinsic electronic & optoelectronic properties of dislocations in diamond. According to general experience with semiconductor materials, high dislocation densities can deteriorate the performance of devices drastically. As a consequence, they are studied intensively and strong efforts are made to minimize their density. Though vigorous activities have been launched to develop diamond-based electronic devices and dislocations have already been identified as major structural defect, our knowledge on their basic properties is rather poor. This is mainly due to the absence of well-defined samples. The group of the applicant has developed a heteroepitaxy technique that recently facilitated the synthesis of a single crystal diamond disc with a diameter of ~90 mm. Their approach has the potential to remove a major hurdle in device development, i.e. the unavailability of wafer-size substrates. In addition, this method enables now the controlled preparation of crystals containing dislocations with defined propagation direction and densities varying over 4 orders of magnitude as required for systematic studies. The planned work will start with a full spectroscopic characterization of samples with defined dislocation densities and line vectors by UV/Vis- and IR-absorption, photoluminescence (PL) and cathodoluminescence (CL). Next, a setup for spectrally resolved photoconductivity (SPC) and thermally stimulated currents (TSC) will be constructed. The subsequent measurements will identify and quantify electrically active defect levels. In the framework of several collaborations, charge collection efficiency (CCE) and charge transient spectroscopy (QTS) measurements will be performed in order to derive density, capture cross section and depth of traps, separately for electrons and holes. Next, the diffusion coefficient and the lifetime of charge carriers will be determined by two pump-probe techniques. Finally, the material will be used to produce devices (detectors, electronic devices). Besides insight in the intrinsic electronic properties of dislocations, critical thresholds for their density in different applications will be derived, that can provide benchmarks for devices development.