Investigation of Ni induced deep levels in N-type Si by a temperature dependence of piezoelectric photothermal signals

The temperature variation of the piezoelectric photo-thermal (PPT) signal intensity of N-type Ni-doped Si was measured in the range from 100 to 300 K. We observed one distinctive peak at 150 K in the Ni doped sample. Since no intense peak could be observed for the control sample, we consider that this 150 K peak is due to Ni impurity. The activation energy, electron capture cross section and concentrations are obtained by fitting the observed curve to that from the theoretical analysis based on the rate equations for electrons. The best-fitted parameters are in good agreement with those obtained by conventional deep defect levels transient spectroscopy (DLTS) measurements. The usefulness of PPT measurements for studying the deep level in semiconductors is pointed out.