Figure 4.

Schematic diagrams of activation of h‐BN and nucleation mechanism of GaN. a) Surface of h‐BN. b) Formation of B—O—N and N—O bonds on h‐BN surface by trapping OH— in HCl solution. c) Desorption of H atoms from activated h‐BN surface (i.e., from N—O—H bonds) during the temperature ramping of substrate. d) Generation of N—O—N bonds on N—O bonds by trapping N atoms. e) Formation of N—O—N—Ga (3) structures by binding three Ga atoms on every N—O—N, indicating the start of Ga‐polarity GaN epitaxy.