TENSILE STRAIN RELAXATION IN GANXP1-X (X-LESS-THAN-OR-EQUAL-TO-0.1) GROWN BY CHEMICAL BEAM EPITAXY

A study of strain relaxation in GaNxP1-x epilayers grown by chemical b eam epitaxy, using a rf-plasma nitrogen radical beam source, tertiaryb utylphosphine, and triethylgallium, is reported. Microcracks are obser ved in GaNxP1-x epilayers grown on GaP when the nitrogen composition i s greater than 1.6%. Transmission electron microscopy results show tha t the tensile-strain relaxation in GaNxP1-x epilayers is initially rel ieved by microcrack formation without misfit dislocations. These micro cracks penetrate through the interface, degrading the crystallinity of the GaP substrate. Microcracks formation can not be alleviated by adj usting the growth rate, growth temperature, V/III ratios, and forward plasma power, but they can be eliminated by reducing the growth area o f the GaP substrate. (C) 1996 American Vacuum Society.