Fig. 6: Van der Waals epitaxy for misfit strain release.

a XRD scans of the 3.0 mm SL and low-temperature buffer AlN samples (upper) and (0002) mapping of the SL sample. b Model of strain control of the AlN template by the introduction of the (AlN/GaN) multi-buffer layer. c (Upper) Single-crystal h-BN release layer growth on sapphire for AlGaN MQWs and (lower) optical image of the blue light EL from the transferred vertical-type LED. d Schematic diagram illustrating the overgrowth process of GaN thick epilayer on the h-BN buffered GaN/sapphire template. e Schematic diagram of the nucleation and film growth of AlN on N₂-plasma-treated graphene/sapphire substrate. f Schematic illustration of morphology evolution for AlN films grown with low-temperature AlN buffer and graphene buffer, respectively. Figures reproduced from a ref. ⁸⁷, © 2002 AIP Publishing; b ref. ⁸⁸, © 2007 Elsevier; c ref. ⁹², © 2012 Springer Nature; d ref. ⁹³, © 2016 Springer Nature; e ref. ⁹⁴, © 2014, American Chemical Society; f ref. ⁹⁶, © 2020, John Wiley and Sons