Diamond mosaic wafers in which several seed crystals are connected laterally by chemical vapor deposition (CVD) are promising large-scale substrates for diamond electronics. One of the prime concerns of the applicability of diamond mosaic wafers is the presence of highly defective coalescence boundaries, which degrade the electrical performance. For Schottky barrier diodes (SBDs), a large leakage current with an inferior Schottky barrier height has been observed at mosaic boundaries. To further improve the device uniformity, high-quality, low-dislocation film growth is required. Here, we introduced a buffer layer to mitigate the influence of coalescence boundaries on diamond mosaic wafers. Diamond film growth by hot-filament CVD accompanied by tungsten incorporation effectively suppressed dislocation propagation from the mosaic substrate to the epilayer. After insertion of the buffer layer, SBDs showed improved rectifying behavior with suppressed leakage current at coalescence boundaries. In addition, the forward/reverse characteristics were essentially identical and high electric breakdown strength exceeding 3 MV cm−1 was demonstrated regardless of the presence of coalescence boundaries when the buffer layer was included.
Dislocations in semiconductor crystals are desirably minimized as much as possible, since their presence typically deteriorates device performance. While diamond electronics have demonstrated superior device properties, they have not fulfilled their material limit yet. To further improve device performance, a low dislocation density and a high-quality epitaxial layer are required. In this study, diamond films are homoepitaxially grown by hot-filament chemical vapor deposition accompanying W incorporations from heated metal-wires. The films exhibited better crystalline quality than seed substrates: a large reduction of threading dislocation from 2 × 106 to 3 × 104 cm−2 was demonstrated. The dislocation propagation was partially annihilated by W impurities. The electrical properties of Schottky barrier diodes after dislocation reduction were highly uniform, improved rectifying actions.
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