Ultrawide-bandgap boron nitride thin films grown on diamond via pulsed laser deposition*

Ultrawide-bandgap (UWBG) semiconductors (bandgap >4.0 eV), such as boron nitride (BN) and diamond, and their epitaxial heterostructures hold significant importance for the development of next-generation high-power radio-frequency electronics. However, achieving in-situ hetero-epitaxy with ultra-clean defect-free interfaces of BN/diamond heterostructures or vice-versa remains extremely challenging due to the complex growth kinetics and stability involved. We have grown BN thin film on single crystal (100) diamonds by using pulsed laser deposition and investigated its structural, magnetic, optical, and thermal properties. In-depth structural analyses (XPS, VBS, Raman, FTIR, and cross-sectional HRTEM, and EELS) confirms the growth of mixed phase BN on diamond, which exhibited diamagnetic behavior at room temperature. Film shows anisotropic refractive index within the visible-to-near-infrared wavelength range. Furthermore, we obtained room-temperature cross-plane thermal conductivity (k_^) of BN is ~1.53 W/mK, whereas thermal conductance of the BN/diamond interface is ~20 MW/m²K. These findings are valuable for a wide-range of device related applications based on UWBG BN/diamond heterostructures.