Lattice parameter study of silicon uniformly doped with boron and phosphorus

Abstract

Powder and single-crystal X-ray techniques have been employed to obtain precise lattice parameters of silicon uniformly doped with boron or phosphorus. Good agreement is found between the two methods. Previous accurate determination of the CuKα₁, effective wavelength has yielded λ=1.540621±0.000006 Å. Particular care has been devoted to the chemical and electrical characterization of the alloys, whose maximum dopant concentrations were 8×10¹⁹ atoms cm⁻³ for P and 4.4×10²⁰ atoms cm⁻³ for B.

A linear dependence of lattice parameter on concentration has been found for P in the whole examined range, while for B a deviation from the linear trend starts at about 2.25×10²⁰ atoms cm⁻³. Tetrahedral radii are found to be 1.176 Å for pure Si, 1.07 Å and 0.91 Å respectively for dissolved substitutional P and B. Values of the linear lattice contraction coefficient, volume size factor, Vegard's law factor and elastic strain energy in both alloys are reported and discussed. The deviation from linear trend in borondoped alloys is analysed and it is shown that the phenomenon is insensitive to heattreatments and does not depend on the degree of ionization of boron atoms.