Statement of the Problem: Presently Si based for Minimum Ionization Particle (MIP) detectors require very low temperature (<-30 C) for the required level of device performance. DoE-HEP is looking for much faster higher radiation resistance radiation detectors that are capable of operation at higher temperatures; i.e., ones based on SiC substrates for future experiments. Hence design and development efforts SiC based detectors, for single charged particles and MIPs with a primary focus on using thick (50-70 um) epitaxy 4H-SiC n-type layers with low-doping (1013 - 1014 cm-3), are needed to realize ultrafast high radiation resistance high temperature operation. The epi-layer should exhibit low on resistance and low leakage current in the reverse bias condition. Ultimately, low gain avalanche diodes (LGAD) based on SiC need to be developed to replace, the present Si based detectors. General statement of how this problem is being addressed: The most important problem addressed here is the growth of thick (>50 um) n-type epitaxial 4H-SiC with low doping (~5x1013 cm-3). SMI has developed proprietary CVD hardware and process technology which yield a growth rate of epi quality 4H-SiC at ~100 um/hr much higher growth rate than reported literature values. Further, the grown epi-4H-SiC n-type layers have low defects < 5 Basal plane dislocations/cm2, and very low morphological defects such as: step bunching carrot defects, ingrown stacking faults, pyramidal and triangular defects (with a root mean square roughness of ~0.4 nm). Our growth temperature is low so as to be much more energy efficient (1350oC i.e., ~250oC lower than the conventional SiC growth). These experiences place our team in a unique position to address the DoE-HEP requirement for SiC substrate-based sensors. Phase I Work: In Phase I wee will carry out (1) Device design/refinement of multi-layer epi-4H-SiC structure which will form the basis of LGAD device will be carried out on collaboration with USC and MSU, (2) CVD growth refinement of thick (50-70 um) epitaxial 4H-SiC with low doping levels (1013 - 1014 cm-3) based on our proprietary process technology will be carried out in Phase I, (3) The CVD grown material will be characterized and resulting data will be used as feedback to improve the quality of the 4H-SiC epi-layers, (4) As a reach task, a prototype intermediate LGAD device will be fabricated at the end of Phase I if time and funds permit, (5) Refine the Phase I plan in response to results achieved. Commercial Applications and Other
Benefits: The anticipated public benefits of this work include technical, economic, social, and other public areas as a whole and advancement in science by advancing the capabilities to understand phenomenon at atomic scale resolution leading to new discoveries. This project will advance the high energy physics sector with the development of high-energy particle accelerators, the possibility to study nuclei, quarks, and gauge bosons using the polarized electron sources presented here. Furthermore, the technology helps in enabling basic energy and medical sciences, better understanding of the universe and also for the US to lead the world in cutting edge technology.
