Characterization of Defect-Dopant Interactions in CVD-Grown Diamond

Dopant incorporation in diamond is crucial for applications in power electronics, radiation detection, and quantum sensing. However, the interplay between inherent defects in diamond epitaxy and dopant segregation, as well as the influence of dopants on defect density is not yet well understood. We have performed correlative microscopies and spectroscopies to gain further insight into dislocation properties and generation mechanisms in boron-doped homoepitaxial CVD-grown diamond. Using site-coincident electron channeling contrast imaging (ECCI) and cross-sectional transmission electron microscopy (XTEM), we demonstrate ECCI as a rapid, non-destructive measure of threading dislocation density that can achieve similar accuracies as XTEM.[1] Dislocations emanated from the highly defective interface, indicating polishing damage as the source of dislocation generation. Two-beam condition imaging reveals that most dislocations have a mixed character (consistent with polishing damage[2]), while some exhibit purely edge or screw quality. By coupling cathodoluminescence (CL) characterization (which had been previously used to characterize dislocation density in diamond[3]) with ECCI, our site-coincident analysis found only 20-40% of dislocations exhibit A-band luminescence. Despite prior reports finding no correlation between Burgers vector and dislocation luminescence[4], our ECCI contrast line analysis indicates a potential correlation between Burgers vector and A-band luminescence. To investigate the role of boron in dislocation luminescence, we performed spatially resolved secondary ion mass spectrometry (nanoSIMS) to track the ¹¹B isotope throughout the diamond layer across regions with varying dislocation density (10⁸ cm^-2 and 10⁷ cm^-2). Using a 100pA Cs⁺ ion beam with estimated spot size of 250nm and detectivity limit of 10¹⁷ cm^-3, we found no difference in boron uniformity among the two distinct dislocation density regions. Prior reports found boron segregation in 2nm-diameter regions surrounding dislocations with density 2-2.5x the background doping density of 10²¹ cm^-3.[5] For our 10¹⁹cm^-3 boron-doped film, we can rule out boron segregation exceeding 10²² cm^-3 solely at the dislocation core (diameter &lt;1nm) and any segregation of 10²⁰ cm^-3 or greater for 10nm diameter regions around the dislocations. We will discuss further correlated XTEM-CL to elucidate the role of Burgers vector in dislocation luminescence and the effects of boron doping on dislocation density and luminescence in films with boron density ranging from 10¹⁹-10²¹cm^-3. Understanding dislocation luminescence mechanisms will aid in the continued development of rapid and accurate dislocation characterization. Further insight into dislocation generation and the interaction between dislocations and intentional dopants like boron will facilitate strategies to reduce dislocation density, advancing the scalability of diamond devices and substrates.<br/> <br/>1. H. Yan, E. Postelnicu, et al., “Multi-microscopy characterization of threading dislocations in CVD-grown diamond films,” Appl. Phys. Lett. <b>124</b>(10), (2024).<br/>2. M.P. Gaukroger et al., “X-ray topography studies of dislocations in single crystal CVD diamond,” Diam. Relat. Mater. <b>17</b>(3), 262–269 (2008).<br/>3. I. Kiflawi, and A.R. Lang, “On the correspondence between cathodoluminescence images and x-ray diffraction contrast images of individual dislocations in diamond,” Philos. Mag. <b>33</b>(4), 697–701 (1976).<br/>4. N. Yamamoto et al., “Cathodoluminescence and polarization studies from individual dislocations in diamond,” Philos. Mag. B Phys. Condens. Matter; Stat. Mech. Electron. Opt. Magn. Prop. <b>49</b>(6), 609–629 (1984).<br/>5. S. Turner et al., “Direct imaging of boron segregation at dislocations in B:Diamond heteroepitaxial films,” Nanoscale <b>8</b>(4), 2212–2218 (2016).