First-principles study of band offsets in ferromagnetic semiconductor heterojunctions

We report valence and conduction band alignments and offsets for heterojunctions between CdCr2Se4, an n-type ferromagnetic semiconductor, and the non-magnetic materials Si and GaAs, evaluated using density functional theory. We explore numerically the impact of different interface features on the type of band alignment and the magnitude of the offsets. For example, we find it is energetically favorable to deplete Cr atoms from the layers at the interface; this also leads to band alignments smaller in magnitude compared to those obtained for Cr-rich interfaces and ideal for electrical spin-injection into either Si or Ga-terminated GaAs substrates.