GROWTH, ELECTRICAL-PROPERTIES AND RECIPROCAL LATTICE MAPPING CHARACTERIZATION OF HEAVILY B-DOPED, HIGHLY STRAINED SILICON-MOLECULAR BEAM EPITAXIAL STRUCTURES

The growth, electrical and structural characterization of heavily B-do ped Si layers produced by molecular beam epitaxy is reported. B doping was obtained from an elemental B source by indirect heating of a grap hite crucible in a thin, meander-shaped graphite heater. High doping l evels up to 9 X 10(20) cm(-3) were achieved in structures which showed excellent epitaxial quality and bulk-like mobilities for growth tempe ratures less than or equal to 500 degrees C. The growth temperature (T -g) dependence of the electrical activation is reported in relation to the dopant incorporation and crystalline quality. At T-g greater than or equal to 600 degrees C and high doping levels, poor electrical act ivation due to dopant segregation and precipitation was observed. The B-induced lattice strain in the Si epilayer was determined by means of a two-dimensional high-resolution mapping of the reciprocal space. Th e lattice contraction coefficient was measured to be (6.3 +/- 0.1) x 1 0(-24) cm(3)/atom by considering the concentration of carriers which s hould be in substitutional positions. Strain characterization of sampl es with strongly reduced electrical activation, i.e. grown at T-g grea ter than or equal to 600 degrees C, showed that the lattice contractio n is related to the effectively incorporated and activated fraction of carriers rather than to the total dopant concentration.