STRUCTURAL CHARACTERIZATION OF LATTICE-MATCHED ALXIN1-XAS INP AND GAYIN1-YAS/INP HETEROSTRUCTURES BY TRANSMISSION ELECTRON-MICROSCOPY AND HIGH-RESOLUTION X-RAY-DIFFRACTION/

In this work we report on transmission electron microscopy and high-re solution x-ray diffractometry studies of lattice matched AlxIn1-xAs/In P and Ga(y)ln(1-y)As/InP epilayers grown by molecular beam epitaxy on InP(100) substrates. High-resolution and diffraction contrast electron microscopy measurements show the presence of different contrast zones in the epilayers. The analysis of high-resolution x-ray diffraction m easurements and computer simulations ascribe these zones to the presen ce of a compositional gradient in the epilayers. A comparison among in vestigated samples grown under slightly different growth conditions co mbined with an analysis of the crystal defects is presented. Growth-in duced small variations in the chemical composition of the epilayer can produce differences in the structural quality of the epitaxial layer. Finally, a few monolayers thick and highly strained film of InAsP, is observed in all investigated samples at the substrate/epilayer interf ace. The formation of this interface layer is explained by the exchang e of As and P during exposure of the InP surface to As-4 before the gr owth. (C) 1995 American Institute of Physics.