Strain-induced splitting in valence band of Si–Ge whiskers

The temperature dependences of resistance for the p-type conductivity solid solution silicon–germanium whiskers doped by boron with concentration of 1 × 1018 cm−3 were investigated in the temperature range of 4.2–300 K and under the uniaxial compressive strain till − 3 × 10–3 rel. un. We studied the strain influence, which was caused on a spin–orbit splitting in the valence band spectrum. As an outcome, the spin–orbit splitting energies for both light and heavy holes were discovered based on the k–p method. The strain-induced effects of solid solution Si0.2Ge0.8 whiskers were studied at low temperatures. Found giant piezoresistive effect at helium temperature gives opportunity to create the supersensitive strain gages on the basis of silicon–germanium whiskers with doping concentration in the vicinity to the metal–insulator transition. The mechanical sensor operating at helium temperature and deformation range of 5 × 10–4–1.3 × 10–3 rel. un. was designed with the sensitive element Si0.2Ge0.8 whiskers doped to concentration 1 × 1018 cm−3.