Nuclear Magnetic Resonance in Indium Antimonide I. The Effect of Impurities

Abstract

A study has been made of the effect of impurities on the 115In nuclear magnetic resonance in indium antimonide. In n-type (Te-doped) and p-type (Zn-doped) samples, the amplitude and width of the resonance are very sensitive to the presence of donors or acceptors, a concentration of 1019 cm−3 reducing the maximum of the derivative of the absorption curve by a factor of 10. This is ascribed to broadening arising from the interaction of the nuclear quadrupole moment with the Coulomb field of the ionized impurity atoms. The effect is slightly less pronounced in p-type than in n-type samples, which can be explained by the fact that holes are more effective than electrons in screening the ionic charges, because of their greater effective mass. Assuming the field gradient at a distance r from an ion to be given by ∂2 V/∂r 2=2βe/r 3, β must be ∼ 350 to fit the experiments, which implies an'anti-shielding factor’ of ∼ 1000. It is suggested that this large value is associated with the smallness of the forbidden gap...