A Study of Defects in GaAs Substrates and GaAs-AlxGa1-xAs DH Epitaxial Wafers by X-Ray Topography

Abstract: Defects in GaAs substrates and GaAs-Alx Ga1-xAs DH (double heterostructure)epitaxial wafers have been observed by means of transmission X-ray topography. Highresolution X-ray topography and metallographic techniques prove that the contrastin X-ray topographic photos is produced by crystal defects.An evaluation for thedensity of the defects in GaAs substrates and GaAs-Alx Ga1-xAs DH wafers is givenaccording to the X-ray topographic photos. The stripe lasers have been made by conventional LPE (liquid phase epitaxy)and proton bombardment. Measurement of the characteristics of the lasers shows thatthe device yield and quality correspond to our evaluation from X-ray topographyfor the density of the defects in the substrates and epitaxial wafers.