Using first-principles calculation for the electronic structures of nm-scale  GaN freestanding films, it is found that the Ga-terminated surface (SGa) has a positive electrostatic potential, while the N-terminated surface has a negative electrostatic potential (SN), so that the energy bands tilt upwards from SGa to SN. Additionally, it is determined that an intrinsic self-regulated charge transfer across the film limits the electrostatic potential difference across the film, which renders the local conduction band energy minimum at SGa approximately equal to the local valence band energy maximum at SN. This effect is found to occur in films thicker than ∼4 nm. If the dangling-bond/surface states at both SGa and SN are passivated by pseudo-hydrogen atoms, the tilt of energy bands is similar, though the cross-film potential is reduced due to the extra H5/4-Ga and N-H3/4 dipole layers.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics