Direct observation of precipitates and self-organized nanostructures in molecuar-beam eipitaxy grown heavily doped GaAs:Si

We report a cross‐sectional scanning tunneling microscopy investigation of heavily Si doped [001]‐oriented GaAs grown by molecular‐beam epitaxy. At a very high doping level (6×1019 cm−3), Si‐doping induced precipitates are directly observed in XSTM images of the as‐grown epitaxial layers. Most of the precipitates are found to have a characteristic oval shape with the long axis (∼80 Å) along the growth direction. In contrast to the low diffusivity of randomly distributed Si dopants in the moderate doping regime, these precipitates are found to be highly mobile and spontaneously form ‘‘nanowires’’ during crystal growth.