Arsenic flux dependence of incorporation of excess arsenic in molecular beam epitaxy of GaAs at low temperature

Incorporation of excess As in GaAs layers grown by molecular beam epitaxy was studied by varying As fluxes for four different substrate temperatures, 210, 240, 270, and 290 degrees C. Concentrations of excess As in GaAs layers were estimated by measuring increases of lattice spacings with x-ray diffraction, and the substrate surface temperature was monitored by using a quartz rod connected to an infrared pyrometer with its end placed in the vicinity of the substrate surface. Nearly stoichiometric GaAs layers without any detectable increase of the lattice spacing are grown at all substrate temperatures under the As atom flux equal to the Ga atom flux. With a slight increase of the As flux from the above stoichiometric condition, the concentration of excess As sharply increases for all substrate temperatures. For the substrate temperature of 210 degrees C, the concentration of excess As is saturated in the range of As atom fluxes more than three times the Ga atom flux, while similar tendencies are observed for other substrate temperatures. The incorporation process of excess As is discussed on the basis of these results. (C) 1998 American Institute of Physics.