Growth of Bulk Diamond by Microwave Plasma Enhanced Chemical Vapor Deposition

Diamond has extreme physical properties such as high thermal conductivity, high carrier mobility, and high breakdown field. In addition, diamond electronics presents high temperature operation, radiation hardness and solar blindness. Because of these properties, they are expected to be utilized in power electronics, UV and radiation sensors and FETs for extreme environments. Large and high-quality diamond wafers are indispensable to realize diamond electronics devices. In this study, we report reduction of the dislocation density using bulk diamond growth by CVD which is developed to enlarge diameter of diamond substrates ^{[1, 2]}.<br/><br/>In {100} growth, which is widely used in diamond CVD growth, most of the dislocations propagate to [001] direction ^{[3, 4]}. Using this feature, we attempted to reduce the dislocation density in diamond by forming orthogonal face to growth direction.^{[2, 3]}. Samples were grown by microwave plasma enhanced CVD. {100} single crystal CVD diamond was used as substrate. First, several-mm thick single crystal diamond was grown on (001). Then (010) plane was sliced from bulk diamond by laser and was mechanically polished. After that, (010) diamond plate was used to evaluate etch pit density. Etch pit was formed using a hydrogen/oxygen plasma etching. Etch pit densities (EPDs) were evaluated using Laser microscope. EPDs of the (010) substrate and those of the epilayer on (010) substrate were the order of 10³-10⁴cm^-2 , which was two order of magnitude lower than that of (100) CVD diamond substrate. In addition, the full width half-width of the XRC (004) curve was improved from 30 arcsec for (100) substrate to 10 arcsec for the (010) substrate. It is shown that three-dimensional bulk diamond growth by CVD is an effective for improving crystal quality while expanding the diameter of {100} single crystal diamond.<br/><br/><b>References</b><br/>[1] H. Yamada et al., Diam. Relat. Mater. 101, 107652 (2020).<br/>[2] Mokuno et al., Diam. Relat. Mater. 14, 1743 (2005).<br/>[3] Mokuno et al., Diam. Relat. Mater. 19, 128 (2010).<br/>[4] I. Freil et al., Diam. Relat. Mater 18, 808 (2009).