Studies of Piezoresistance and Piezomagnetoresistance in Si Whiskers at Cryogenic Temperatures

Abstract

The temperature dependence of the electrical resistance of silicon whiskers was studied as their piezoresistance and piezomagnetoresistance at 4.2 K. A special technique was developed to study the whiskers in compressive and tensile strain. It was observed that the thermal strain due to the mounting of the whiskers on different substrates at helium temperatures may be high enough to ‘throw’ a crystal from the metallic side of the metal-insulator transition to insulating one and vice versa. A negative magnetoresistance in p-type silicon whiskers was found at 4.2 K, but in uniaxial compression a transition from negative magnetoresistance to ‘anomalous’ positive magnetoresistance was observed. The possibility to apply a ‘giant’ piezoresistance found in the vicinity of the metal-insulator transition in strain gauges and pressure sensors having a very high sensitivity to the measured value is discussed.