Flow Modulation Epitaxy of Thick Boron Nitride Epilayers and Wafer-Level Exfoliation

Abstract

Uniform and continuous wafer-level sp 2 -hybridized boron nitride (sp 2 -BN) is essential for the development of other III-nitride semiconductors in alleviating lattice mismatch and constructing flexible devices. In this work, we realize wafer-level thick sp 2 -BN on 2 in. c-plane sapphire with a flow modulation epitaxy (FME) method by metal−organic chemical vapor deposition (MOCVD). It is revealed that the pulsed ammonia and triethylboron interruptions greatly improve the surface morphology and crystalline quality of sp 2 -BN, attributed to the unintentional nitridation, the decrease of C impurity concentration, and the increase of B atom surface mobility. The root-mean-square roughness of 6.5 nm sp 2 -BN is only 1.6 nm, and the full width at half-maximum of the Raman spectrum is only 31.18 cm −1 . Besides the flat morphology with uniform wrinkles, a well-ordered layered sp 2 -BN structure with a lattice spacing of 0.34 nm is also revealed. Furthermore, thick sp 2 -BN demonstrates controllable exfoliated characteristics due to a weak interfacial force. These findings highlight the comprehension of the growth behavior and exfoliated characteristics of sp 2 -BN on the sapphire substrate and provide opportunities for flexible nitride devices in mass production.