Polarization-induced valence-band alignments at cation- and anion-polar InN∕GaN heterojunctions

The authors show that the existence of polarization discontinuities at polar III-nitride heterointerfaces can lead to large core-level shifts of photoelectrons and modification of apparent valence-band offsets. In this letter, large Ga core-level shifts, resulting from the interface dipole fields, have been directly measured by photoelectron spectroscopy on In∕Ga-polar (0001)- and N-polar (0001¯)-oriented InN∕GaN heterojunctions with monolayer abrupt, nearly fully relaxed lattices. Combined with the photoelectron spectroscopic measurements of InN and GaN bulk epilayers, the determined valence-band offsets are 1.04 and 0.54eV for In∕Ga- and N-polar heterojunctions, respectively.