Basic electronic and optoelectronic properties of threading dislocations in heteroepitaxial diamond

该提案旨在全面研究金刚石中位错的本征电子和光电子性质。根据半导体材料的一般经验，高位错密度会大大降低器件的性能。因此，人们对它们进行了深入的研究，并作出了很大的努力来减少它们的密度。虽然人们已经开始大力开发金刚石基电子器件，并且位错已经被确定为主要的结构缺陷，但我们对其基本性质的了解却相当贫乏。这主要是由于缺乏定义良好的样本。申请人小组开发了一种异质外延技术，最近促进了直径约90毫米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一个主要障碍，即晶圆尺寸基板的不可用性。此外，这种方法现在可以控制制备含有位错的晶体，其传播方向和密度在系统研究所需的4个数量级以上。计划中的工作将从通过UV/Vis和ir吸收，光致发光（PL）和阴极发光（CL）对具有确定的位错密度和线矢量的样品进行全光谱表征开始。接下来，将建立光谱分辨光电导率（SPC）和热刺激电流（TSC）的设置。随后的测量将确定并量化电活动缺陷的水平。在几个合作的框架内，电荷收集效率（CCE）和电荷瞬态光谱（QTS）测量将被执行，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，将用两种泵浦探针技术确定载流子的扩散系数和寿命。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内在电子特性外，还将推导出不同应用中其密度的临界阈值，这可以为设备开发提供基准。

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.