OPTICAL-PROPERTIES OF INGAAS LINEAR GRADED BUFFER LAYERS ON GAAS GROWN BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

We report optical characteristics of linear graded InxGa1-xAs (X(In) = 0-0.58) buffer layers grown on GaAs by low-pressure metalorganic chem ical vapor deposition. Two types of wirelike surface structures were o bserved from the layers grown at two different temperatures. Low-tempe rature photoluminescence (PL) and double-crystal x-ray diffractometric measurements indicate that the PL energy and the relaxation of the gr aded layers were strongly dependent on the top surface structure. InGa As cap layers were grown on top of the graded buffer layers with a var iation of indium composition. A strong PL signal was observed from the top region of the graded layer grown with a lattice-matched cap layer . It suggests that the top region of the grade, similar to a graded we ll structure, is compressively strained but is of high structural qual ity without dislocations. (C) 1996 American Institute of Physics.