Growth and characterization of lattice-matched CaxSr1−xF2 on GaAs(100)

Abstract

The epitaxial growth and characterization of the structural, morphological, interfacial, and electrical properties of lattice-matched Ca0.43Sr0.57F2 on GaAs(100) are reported here. The ∼200 nm films were grown at 500 °C on the GaAs(100) substrates that had been cleaned by annealing at 600 °C. Nomarski optical microscopy, transmission electron microscopy (TEM), scanning electron microscopy, and reflection high-energy electron diffraction results showed that the films were smooth and crackfree, with good crystalline quality. TEM showed evidence of two general types of extended defects in the film which occur at or near the film/substrate interface region. Film resistivity was found to be (3.6±0.75)×1013 Ω cm, and the breakdown field strength was (5.8±1.4)×105 V/cm. However, the breakdown in this case represented a nondestructive conduction process, as opposed to the catastrophic and irreversible change observed in previous studies. The dielectric constant of the films was measured to be 7.43±0.22. Capacitance-voltage measurements indicated that there could be a high density of surface states at the interface that pin the Fermi level within the gap region.