Lateral and Vertical Heterostructures of h-GaN/h-AlN: Electron Confinement, Band Lineup and Quantum Structures

Lateral and vertical heterostructures constructed of 2D h-GaN and h-AlN display novel electronic and optical properties and diverse quantum structures to be utilized in 2D device applications. Lateral heterostructures formed by periodically repeating narrow h-GaN and h-AlN stripes and direct-indirect characters of the band gaps and their values vary with the widths of these stripes. However, for wider sizes, 1D multiple quantum well structures can be generated with confinement of electrons and holes. Vertical heterostructures formed by thin stacks of h-GaN and h-AlN are composite semiconductors with tunable band gap. However, depending on the stacking and number of layers, the vertical heterostructure can transform into a junction, which displays staggered band alignment. Despite the complexities due to confinement effects and charge transfer across the interface, the band diagrams of the heterostructures are conveniently revealed from the electronic structure projected to the atoms or layers. It is also shown that the optical properties attained in lateral and vertical heterostructures are rather different from their single-layer parent constituents.