Interaction of Acoustic Waves with Acceptor Holes in Silicon: The Influence of Internal Stress

The temperature and the magnetic field dependences of the ultrasonic attenuation are measured at low temperatures in lightly doped $p-\mathrm{S}\mathrm{i}$ samples with various impurity concentrations and dislocation densities. In the dislocation-free sample, a peak is found in the temperature dependence, which is related to the content of acceptors. In the sample with high dislocation density (2 × ${10}^4$ ${\mathrm{cm}}^{-2\mathrm{}}$), an additional attenuation is found below 3 K which is ascribed to the resonance absorption by acceptor holes and the attenuation is quenched with a lower magnetic field (about 10 kG) than that in the dislocation-free sample. It is also found that the stress caused by an In-bonded quartz-plate transducer changes the attenuation remarkably below 3 K. Therefore ZnO piezoelectric thin films were used in the present study. The observations are explained semiquantitatively in terms of the acceptor-hole-lattice interactions in the effective-mass approximation by taking the distribution of the internal stresses into account after Suzuki and Mikoshiba. The apparent difference in the contributions to the attenuation from the correlation among the impurities and from the dislocations is ascribed to the differences in the distribution of the internal stresses. It is pointed out that the degeneracy of the acceptor ground state is lifted even in the samples with boron content of 5 × ${10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$ because of the electronic correlations among the randomly distributed impurities.