The effect of stress and strong magnetic fields on the shallow impurities in semiconductors and the piezoresistance and magnetoresistance for hopping conduction

Abstract

The effects of uniaxial strees and strong magnetic fields on hopping conduction in lightly doped semiconductors are reviewed. The piezoresistance and magnetoresistance are interpreted in terms of modification of the shallow impurity states, making extensive use of the results of percolation theory. It is shown that our present understanding of the stress effects on shallow donor and acceptor states provides an adequate explanation of piezoresistance in both n- and p-type semiconductors. The effects of the magnetic field on the donor states are known sufficiently well to account for the magnetoresistance. However, the magnetoresistance in p-type semiconductors remain largely unexplained owing to the lack of detailed knowledge of magnetic field effects on shallow acceptor states.