Structural reconstruction and visible-light absorption versus internal electrostatic field in two-dimensional GaN–ZnO alloys

GaN-ZnO alloys are more promising semiconductors than their counterparts for optoelectronic applications due to the abrupt red shift in the visible-light range. Unfortunately, the strong internal electrostatic field (IEF) seriously hinders to further improve the optoelectronic performance due to the charge density of surface states. We point out a structural model to extremely improve the visible-light absorption by overcoming the bottleneck of the IEF in the two-dimensional (2D) nonisovalent alloys. The novel haeckelite (8|4) configuration with the nearly zero IEF shows much better optoelectronic performances than the conventional wurtzite configuration. Meanwhile, we explore the thickness-driven structural transitions from the planar hexagonal to the 8|4 and to the wurtzite configurations. The visible-light absorption efficiency quickly rises up from the bulk wurtzite to the bulk 8|4 to the 2D 8|4 and to the MoS2-based heterostructures with the different-layer 8|4 configurations. The heterointerfacial coupling is an effective way to further reduce the IEF and hence to significantly improve the visible-light absorptions by enlarging the population of band edge states in the 8|4 configuration. We suggest that the 8|4 configuration is more prospective for diverse optoelectronic applications in 2D GaN-ZnO alloys than in binary counterparts.