USING SYNCHROTRON-RADIATION X-RAY MULTIPLE DIFFRACTION TO EXAMINE THELATTICE COHERENCY OF SEMICONDUCTOR SURFACES AND EPITAXIAL LAYERS

An experimental facility for carrying out x-ray multiple diffraction ( XRMD) studies in parallel-beam geometry using the Daresbury synchrotro n radiation source and its application in the study of coherency of an epilayered sample are described. Experimental high-resolution Renning er scans (RS) about GaAs(006) are presented and the pseudoforbidden '' Aufhellung'' eight-beam (000,006,020,042,044,026,<0(2)over bar4>,<0(2) over bar2>) case has been fully resolved for the first time using the setup which involves a double-crystal six-circle scattering geometry a nd data acquisition providing optimal conditions for these scans to be obtained. A sample of InGaAs/AlGaInAs/InP (001) epilayered material w as also examined and high-resolution RS from the bulk, substrate, and epitaxial overlayers were obtained. The diffraction wavelength used wa s determined directly from the bulk RS as lambda=(1.4695+/-0.0005) Ang strom. The data clearly reveal a number of interesting XRMD features w hich allow for the sample characterization. The layer parallel lattice parameter can be determined either from the epilayer tetragonal disto rtion in the layer RS or from the MORSI (modulation of the RS intensit y due to the presence of the epilayers) [Greenberg & Ladell, Appl. Phy s. Lett. 50, 436 (1987)] dips in the substrate RS. These dips can also provide simultaneous information on relative tilt and rotation betwee n both layer/substrate lattices. The fitting of the position and profi le of the three-beam surface peaks allows the determination of the lay er parallel lattice parameter and the layer mosaic spread on the sampl e surface plane. (C) 1996 American Institute of Physics.