<i>In situ</i> metal organic chemical vapor deposition of ultrathin sp2-bonded boron nitride dielectric on gallium nitride

Boron nitride (BN) is one of the best dielectric materials for two-dimensional materials due to its van der Waals bonding, ultrawide bandgap, and dielectric and breakdown properties. For conventional semiconductors materials, such as GaN, BN may offer many of these same advantages. Here, we report on in situ metal organic chemical vapor deposition of few nanometer thick sp2-bonded BN on GaN and AlGaN/GaN structures. To achieve high-quality BN/GaN interfaces, growth temperature and time were optimized to achieve thin and smooth BN layers with minimal impact on the GaN layer. At a growth temperature of 1060 °C for 15 min, continuous 4 nm thick BN layers with surface roughness as low as 0.35 nm were achieved. Current-voltage (IV) measurements of BN on n-type GaN metal-insulator-semiconductor (MIS) diodes showed significantly reduced reverse leakage and lower ideality factors compared to Ni/GaN Schottky diodes. From capacitance-voltage (CV) measurements, a built-in voltage of ∼2.2 V was measured, which is consistent with the BN/GaN band offset determined by x-ray photoelectron spectroscopy. The deposition of BN on AlGaN/GaN structures showed minimal degradation of the two-dimensional electron gas transport properties. IV and CV measurements of BN/AlGaN/GaN MIS diodes showed a 3600 times reduction in the reverse leakage current compared to a standard Schottky and had hysteresis less than 0.1 V.