  Wide and ultrawide-bandgap semiconductors lie at the heart of next-generation
high-power, high-frequency electronics. Here, we report the growth of
ultrawide-bandgap boron nitride (BN) thin films on wide-bandgap gallium nitride
(GaN) by pulsed laser deposition. Comprehensive spectroscopic (core level and
valence band XPS, FTIR, Raman) and microscopic (AFM and STEM) characterizations
confirm the growth of BN thin films on GaN. Optically, we observed that BN/GaN
heterostructure is second-harmonic generation active. Moreover, we fabricated
the BN/GaN heterostructure-based Schottky diode that demonstrates rectifying
characteristics, lower turn-on voltage, and an improved breakdown capability
(234 V) as compared to GaN (168 V), owing to the higher breakdown electrical
field of BN. Our approach is an early step towards bridging the gap between
wide and ultrawide-bandgap materials for potential optoelectronics as well as
next-generation high-power electronics.
