Spatial distribution of 0.68-eV emission from undoped semi-insulating gallium arsenide revealed by high resolution luminescence imaging

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Abstract
The luminescence properties of undoped semi-insulating liquid encapsulated Czochralski-grown GaAs ingots have been characterized with ∼3-μm spatial resolution using a scanning electron microscope based, cathodoluminescence (CL) system. The use of a cryostat operating at ∼6 K with cooled PbS and Ge detectors for midgap luminescence imaging has revealed for the first time a depletion in the 0.68-eV emission from zones ∼20 μm wide adjacent to individual polygonized dislocation arrays known as cell walls. These midgap luminescence results have been correlated with band edge CL images of cell structures and with dislocation images obtained using double crystal x-ray topography. It is concluded that dislocation arrays attract or getter the defect centers responsible for the 0.68-eV emission in undoped semi-insulating GaAs, as opposed to generating them.