SELF-ORGANIZED INPLANE INCORPORATION OF SI ATOMS IN GAAS BY MOLECULAR-BEAM EPITAXY

The preferential attachment of Si atoms at misorientation steps on vic inal GaAs(001) surfaces has been studied by RHEED. By analysing the ti me evolution of the specular beam intensity and the change in surface reconstruction during Si deposition we show that a self-organized Si i ncorporation along the step edges takes place. The observed (3 x 2) st ructure is due to an ordered array of dimerized Si atoms with missing dimer rows. Taking into account the structure of the (3 x 2) unit mesh and its orientation with respect to the As-terminated or Ga-terminate d steps, a characteristic minimum in the RHEED intensity recording cor responds to the number of Ga step-edge sites. Since the preferential p ath for Ga as well as for Si adatom diffusion is along the [110BAR] di rection, the critical terrace width for wire-like Si attachment is muc h larger for a misorientation toward (111BAR)As than for a misorientat ion toward (111)Ga. Despite the high local impurity concentration, the Si-modified surface can be overgrown with GaAs without adverse effect s on the growth front. This is promising for the fabrication of doping wires.