GALVANOMAGNETIC EFFECT FOR HOLES AND THE VALENCE BAND IN (001) SILICON ON SAPPHIRE

Magnetoresistance (MR), anisotropy measurement previously performed at room temperature for 1-2 µm thick p-type (001) silicon on sapphire (SOS) has been extended down to 77 K. In order to explain these anisotropies, the valence band structure is numerically calculated by the k-p method along with deformation-potential-constant formalism assuming the lateral compressive strain (∼4 × 10−3) in silicon. In the four 〈110〉 directions for the upper strain-split mJ = ±3/2 band, the derivative (dE/dk2) becomes very small at hole energies above ~10 meV, resulting in a tetragonally-warped, constant-energy surface with four long 〈110〉 protrusions, which may be responsible for room-temperature “four 〈110〉-ellipsoid-like” MR anisotropies. Although low-temperature MR anisotropies cannot be explained in terms of the low-energy ellipsoid, the high hole mobility which exceeds the electron one (A. C. Ipri: Appl. Phys. Lett. 22 (1973) 76) may be due to rapid decrease of hole effective mass to the ellipsoidal one. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.