Characterisation of Stoichiometry in GaAs by X-Ray Intensity Measurements of Quasi-Forbidden Reflections

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Abstract
Deviation from stoichiometry in GaAs was detected in an accuracy of c Ga-c As=3×10-5 by measuring variations of integrated intensities of weak quasi-forbidden reflections of X-rays. Fairly large deviations of the order of 10-4 with higher atomic concentrations in As lattice planes were found for undoped semi-insulating liquid-encapsulated Czochralski (LEC) grown crystals compared with horizontal Bridgaman (HB) grown ones. The radial distribution of the deviation in a wafer was observed to have a total correlation with the distribution of dislocations. Capability of the method is demonstated by results obtained for epitaxial layers grown by VPE, LPE and MBE.