Schottky barrier diodes fabricated on diamond mosaic wafers: Dislocation reduction to mitigate the effect of coalescence boundaries

Abstract

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.