Structural characterisation of amorphised compound semiconductors

Extended X-ray absorption fine structure (EXAFS) has been utilized to measure implantation-induced structural modifications in amorphous GaAs and InP. Relative to crystalline standards, increases in bond length were apparent for both materials. However, the constituent atoms were under- and over-coordinated in amorphous GaAs and InP, respectively, as consistent with the reported decrease and increase in density, respectively. For GaAs, experimental evidence for the presence of homopolar bonding in the amorphous phase was apparent though the similarity in atomic number of the two constituents inhibited a quantitative determination. In contrast, homopolar bonding in amorphous InP was readily measurable - In-In bonding comprised ∼14% of the total In bonds. For amorphous GaAs, all structural parameters were independent of ion dose and implantation temperature as consistent with an intrinsic rather than an implant-specific extrinsic structure.