The advanced unified defect model and its applications

Abstract

The advanced unified defect model (AUDM) is presented for GaAs interfaces with metals, other semiconductors, and insulators. The key defect is the As Ga anstisite, which is also responsible for EL-2 and semi-insulating GaAs. The energy levels of the As Ga antisite (0.75 and 0.52 eV) correspond well with the previously identified energy levels (0.75 and 0.5 eV) of the unified defect model (UDM). Using the AUDM, it is shown that a wide range of experimental data can now be explained. The Fermi level position on GaAs(001) MBE surfaces and its dependency on As or Ga are explained. The changes in Schottky barrier height of LaB 6/GaAs, Al/GaAs, and Au/GaAS on annealing are explained in terms of As Ga antisite density near the interface being increased or decreased due to the annealing. For Al and Au this is correlated with the metal/semiconductor interfacial chemistry, and a predictive capability is developed in terms of net increase or decrease of As at the interface due to this reaction. The Fermi level pinning behavior at low temperature is also explained in terms of this model.