Optical and electrical properties of the disordered composite semiconductor (GaAs)1?x (SiC2 : H)x, grown by metal-organic chemical vapour deposition

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Abstract
Thin semiconducting composite (GaAs)1−x(SiC2 : H)x films with x≤0·32 have been prepared by metal-organic chemical vapour deposition (MOCVD) from ClEt2Ga.AsEt2 and Si(CH2−C ≡ CH)4 as precursors. These materials exhibits an inhomogenous structure consisting of c-GaAs microcrystallites, amorphous GaAs and amorphous SiyC1−y : H with y≃0·33. Optical and electrical properties have been interpreted using a multi-zone model. Optical absorption occurs mainly in the a-GaAs while photoluminescence involves both the c-GaAs and the a-SiyC1−y : H regions. Electrical conduction seems to be controlled by the crystalline or the amorphous part of GaAs according to the volume fraction of a-SiyC1−y : H. Near the film composition x≃0·2, an abrupt variation of the electrical and optical parameters suggests isolation of GaAs microcrystallites previously connected by the amorphous GaAs phase. Above this composition, the conductivity is limited by transport through the a-GaAs connective tissue and so becomes sensitive to an increase in the defect density and/or relative volume of this disordered zone.