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.
M. Danielewski, R. Filipek, R. Kozubski, W. Kucza, P. Zieba, Z. Zurek
N. T. Bagraev et al., "p+-CdB2 - n-CdF2 and p+-Si - p-CdB2 - n-CdF2 Diffusion Heterostructures", Defect and Diffusion Forum, Vols. 237-240, pp. 1060-1065, 2005