Nikolai T. Bagraev

Fractal Self-Assembled Nanostructures on Monocrystalline Silicon Surface

We present ultra-shallow diffusion profiles performed by short-time diffusion of boron from the gas phase using controlled surface injection of self-interstitials and vacancies into the ntype Si(100) wafers. The diffusion profiles of this kind are found to consist of both longitudinal and lateral silicon quantum wells of the p-type that are self-assembled between the layers of microdefects, which are produced by previous oxidation. These layers appear to be passivated during short-time diffusion of boron thereby forming neutral d - barriers. The fractal type selfassembly of microdefects is found to be created by varying the thickness of the oxide overlayer, which represents the system of microcavities embedded in the quantum well plane.

p+-CdB2 - n-CdF2 and p+-Si - p-CdB2 - n-CdF2 Diffusion Heterostructures

The ionic semiconductor CdF2 that is of extraordinary interest for the modern optics and optoelectronics because of the largest band-gap value, 7.8 eV, from all wide-gap semiconductors and of the n-type conductivity caused by doping with the III group elements and subsequent thermal colouring is used to prepare the ultra-shallow p+- n junctions and p+-Si - n-CdF2 heterostructures by the short-time diffusion of boron from the gas phase. The forward branches of the I-V characteristics of the quantum-size p+-n junctions and heterostructures are shown to reveal not only the CdF2 gap value, but also the CdF2 valence band structure as well thereby identifying the ballistic character of the transport of holes. The studies of the I-V characteristics under the voltage applied along the p+-n junction plane demonstrate the metal conductivity of the two-dimensional hole gas, which seems to be evidence of the formation of the p-CdB2 compounds on the n-CdF2 surface in the process of doping with boron.