Multiscale interactions bewteen extended defects and growth front - the case of SiC solution growth – MINTEX

Energy saving as well as efficient energy management is seen as one of the key issues to postpone the warming of the global climate system. Today 40% of all energy consumption is electrical energy, with increasing tendency in future. Therefore power electronics plays an important and growing role in order to control the energy flow between source, load and temporary storage. By using power electronics there is a tremendous potential to save energy in motor drives which today share 50-60% of all electrical energy consumption in the developed world. Along this line, a Silicon Carbide (SiC) based power electronics appears as one of the most promising and realistic choice for the future. However, the SiC technology still suffers from the availability of low cost high quality SiC wafers. As a rule, the current industrial bulk growth process (seeded sublimation or more generally growth from the vapour phase) still presents a poor yield, with almost no hope of dramatic improvements, in terms of extended defect density. Actually, there exists a lot of intrinsic limitations related to the sublimation process, such as i) non stationary concentration fields in the growth cavity, ii) very high temperature and high temperature gradients, iii) high supersaturation. These points directly impact the control of the process, the structural quality of crystals and the doping homogeneity. To sum up, sublimation hegemony is the fruit of SiC long history but it is also objectively the worse method to obtain a 'defect free' crystal. We propose in this project to develop a totally disruptive approach, which is intrinsically able to solve, once for all, the problems related to the bulk growth of SiC crystals. The main goal is to demonstrate the possibility to grow a 'defect free' SiC crystal. Along this line, the project aims at investigating all the scientific and technological building blocks necessary to develop a high temperature solution growth process. The different points which will be addressed are ' The demonstration of a process which is intrinsically up scalable. ' The growth of 'perfect' 4H and 6H-SiC single crystals. With this aim in view, a detailed investigation of defect nucleation, evolution and elimination will be conducted. The focus will be oriented to the multiscale interaction between the growth front and the extended defects. ' The development of other SiC crystal structures of interest (3C-SiC). ' The validation of the 'perfect' wafers through the deposition of an active epilayer by vapour phase epitaxy (VPE). The scientific program is composed of 5 tasks, all running in parallel and scored by the project coordinator. The conditions to succeed are i) to get a complete understanding of macroscopic and microscopic interactions between extended defects and the proceeding growth front (tasks 3&4), ii) to link these phenomena with the growth process itself (task 2), iii) based on these two previous steps, to select the most appropriate growth conditions (process parameters, growth direction, adapted growth mode ') so as to avoid or eliminate any extended defects and iv) to form an epilayer as a validation of the bulk crystal quality (task 5). For the three scientific tasks (2,3 and 4), special care will be taken in modelling the different phenomena, in order to provide both a qualitative but also a quantitative description of the phenomena. Task 1 is only technical; it merges all the technical works necessary for an efficient implementation of the scientific program. The project team gathers all the competences to implement a global strategy coupling experimentation-modelling and characterization. The scientific and technical outputs are very important as this project addresses many fundamental aspects on crystal growth process engineering, and also on interaction between extended defects and the proceeding growth front. Even if the entire project is focused on SiC, it also addresses general phenomena and general rules which have to be thoroughly studied. This kind of research usually develops a very important know-how. A special attention will be paid in integrating this know-how, keeping in mind and probable industrial exploitation. In case of success, there is no doubt that this project will be a scientific and technological breakthrough in the long SiC history and that it will catch the whole academic and industrial community interest.