Detection and origins of crystal defects in GaAs/GaAlAs LPE layers

Abstract

We report the discovery that shallow growth pits develop on the surfaces of GaAs/GaAlAs double-heterostructure wafers prepared by liquid phase epitaxy where the surfaces are intersected by crystal defects. The growth pits enable nondestructive defect characterization of such wafers to be made by optical microscopy. It is found that pits due to stacking faults are more readily detected than pits due to undissociated dislocations. The results of a search for the origins of the defects in the material are also presented. Characteristic "star" patterns develop when the material is etched. TEM observations show that these are due to clusters of crystal defects which originate at inclusions buried in the grown material.