Use of the lateral photoeffect to study sample quality in GaAs/AlGaAs heterostructures

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Abstract
We have used the lateral photoeffect to image the variations in the conductivity of a two-dimensional electron gas (2DEG) setup in a GaAs/AlGaAs heterostructure. A description of the experimental arrangement is given and a simplified theory of the image contrast is presented. Our experiments image contrast resulting from defects such as cracks in the GaAs sublayer, and other contrast resulting from local changes in resistance of the 2DEG. Such variations have important consequences concerning both the interpretation of average parameters measured on such 2DEGs and the performance of electronic devices ( such as high electron mobility transistors ) fabricated using them. The inhomogeneities no doubt have their origin either in defects in the substrate used, or in the growth of the layers, or both.