Characterization of iron based precipitates in GaAs layers grown by molecular-beam epitaxy

GaAs layers that contain small Fe-based precipitates have been grown using molecular-beam epitaxy. The layers were produced either by codepositing Fe during GaAs growth or by first depositing a thin layer of an Fe-Ga alloy and then growing a capping layer of GaAs. Microstructural characterization of the layers was performed by using transmission electron microscopy. For those samples in which the Fe alloy layer was deposited, the layer disappeared after GaAs growth, leaving behind Fe-containing precipitates distributed throughout the GaAs overlayer. Precipitates were also formed in Fe codeposited samples. The sizes and number densities of the precipitates were dependent on the growth method used, with mean diameters ranging from 21 to 47 nm and number densities from 10¹³-10¹⁵ per cm³. The phase, orientation, and morphology of the particles were also dependent on the growth conditions used, with FeAs and Fe being observed.