Composition and texture of thin films grown under 1 bar of fluorine at the surface of GaAs

Abstract

The composition and texture of thin films obtained by the fluorination of GaAs(100) plates under 1 bar of fluorine are investigated by several complementary analysis techniques (Rutherford backscattering spectrometry, IR absorption and scanning tunnelling electron microscopy). They greatly depend on the fluorination temperature Tf and time tf. For Tf ≤ 300 °C, a significant oxygen content and a fluorine deficiency due to water absorption are observed after the layers have been exposed to air. However, for Tf ≤ 400 °C, the composition of coating thin films is GaF3 and does not change after the samples have been aged in moist air for several weeks. In this last instance, up to tf = 1 h which corresponds to 100nm thick fluoride layers, their thickness seems to be homogeneous, but for tf > 1 h, it is demonstrated that the fluorine diffusion, and consequently the thickness of the films, becomes inhomogeneous. © 1991.