The Diffusion Mechanism in the Formation of GaAs and AlGaAs Nanowhiskers during the Process of Molecular-Beam Epitaxy

The formation of GaAs and AlGaAs nanowhiskers using molecular-beam epitaxy on GaAs (111)B surfaces activated with Au is theoretically and experimentally studied. It is experimentally shown that nanowhiskers whose length exceeds the effective thickness of the deposited GaAs by an order of magnitude can be grown. It is found that the experimental dependences of the nanowhisker length L on its diameter D can differ radically from those observed in the case of a vapor-liquid-solid growth mechanism. The L(D) dependences obtained in this study are decreasing functions of D. The above effects are related to the existence of the diffusion transport of atoms from the surface towards the tips of the whiskers, which leads to a considerable increase in the growth rate of thin whiskers. A theoretical model of the formation of nanowhiskers in the process of molecular-beam epitaxy is developed. The model provides a unified description of the vapor-liquid-solid and diffusion growth mechanisms and qualitatively explains the experimental results obtained