Distribution model of arsenic antisite defects in LTG:GaAs Original Research Article

Un-annealed, as-grown low-temperature-grown gallium arsenide (LTG:GaAs) has high concentration of arsenic antisites AsGa, which form a band of midgap states. The defect states are not of EL2, because their density is much higher than that of EL2. A set of defect distribution models is developed, based on the experimental observations with the scanning tunneling spectroscopy. The model set can be used to describe the position of the bulk Fermi level as a function of the compensation degree, enabling the calculation of various electrostatic quantities of the LTG:GaAs. The model set uses the interpolation technique to incorporate the known scanning tunneling spectroscopy results of LTG:GaAs with different dopants and dosages. It also incorporates the Coulomb gap and Hubbard correlation in the distribution of the density of states. Therefore, it is able to handle Si-doped n-LTG:GaAs and Be-doped p-LTG:GaAs. The independent experiments on the bulk resistivity and the surface electric field are used to verify the model set. The application of the model set to the non-alloyed micron-scale ohmic contact with LTG:GaAs proves to be successful, and its implication of un-pinned Fermi level at the interface of LTG:GaAs and n-GaAs is verified by the experiments.