GROWTH AND CHARACTERIZATION BY X-RAY-DIFFRACTION OF GAP INP SHORT-PERIOD SUPERLATTICES/

X-Tay diffraction was used to structurally characterize symmetrically strained GaP/InP short-period superlattices grown on GaAs(001) substra tes by atomic layer molecular beam epitaxy. The possibility of growing highly strained semiconductors layers (with misfit values of -3.6% fo r GaP and 3.8% for InP with respect to GaAs) without relaxation by mis fit dislocations is studied for the case of the GaP/InP material syste m. Three different types of superlattices were grown to study their st ructural properties: (GaP)N(InP)M (N = 2, M = 2 or 3; N = 3. M = 3 or 4) with total thickness of 200-250 nm (set A), 50 nm (set B), and abou t 8 nm (set C). Superlattices of set C samples contain only 5-7 period s and are embedded between two Al0.7Ga0.3As cladding layers. Conventio nal theta-2theta and high-resolution X-ray diffractometry were used to determine the period of the superlattices. in-plane and perpendicular strains (epsilon(parallel-to) and E(perpendicular-to)), chemical comp osition (N, M) and relaxation status of the different layers. The X-ra y interference effect technique was used for the first time to analyze GaP/InP superlattices. We discuss the possibilities and limitations o f this technique applied to structures of this type. The agreement bet ween experimental and simulated diffraction patterns is very good, ind icating the high quality achieved in the growth of this highly straine d material system.