HIGH-RESOLUTION X-RAY-DIFFRACTION STUDIES OF ALGAP GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

High-resolution x-ray measurements have been performed to study the lattice deformation and the Al composition determination of AlGaP grown on (100) GaP by gas-source molecular-beam epitaxy. By using {511} asymmetric reflections, lattice constants in both the growth direction a⊥ and the growth plane direction a∥ were determined. The results show that the AlGaP unit cell deforms from cubic to tetragonal with a⊥ being larger than a∥, and that correlations are needed when using x-ray (400) reflection to determine the Al composition. By using the elastic theory and Rutherford backscattering spectrometry technique, the Al mole concentration and its relationship with the perpendicular lattice mismatch measured from x-ray (400) reflections have been determined.