Synchrotron X-ray topography study of defects in epitaxial GaAs on high-quality Ge

Crystal defects of GaAs thin films deposited by metalorganic vapour phase epitaxy on high-quality Ge substrates are studied by synchrotron X-ray topography. The GaAs thin films were measured to have ≈500 dislocations cm-2cm-2, which is a similar number to what plain Ge substrates show. The dislocation densities measured are also smaller than, for instance, those of high-quality vapour pressure controlled Czochralski grown GaAs wafers, which typically have dislocation densities of ≈1500cm-2. The GaAs films grown on both sides of two-sided substrates display very good crystal quality throughout the sample.