High resolution deep level transient spectroscopy applied to extended defects in silicon

Deep level transient spectroscopy (DLTS) and high resolution Laplace DLTS (LDLTS) have been applied to p-type Czochralski silicon that contains dislocations that have and that have not been locked by oxygen. The stress-induced dislocations have been immobilized by oxygen during heat treatment, which prohibits glide under certain applied shear stresses. The DLTS spectra show typical broad features between 100 and 320 K, characteristic of those seen in other dislocated silicon reported in the literature, and several components are present in the LDLTS spectra. In addition, DLTS spectra show a sharp narrow peak at 40 K at a rate window of 200 s-1 in the case of the locked dislocations, but not in the case of the sample where there is no oxygen locking. LDLTS shows that this deep level consists of more than one component and it is proposed that this peak is likely to be due to electrical activity associated with oxygen at the dislocation core. For hole emission at temperatures above 100 K, in the sample with unlocked dislocations, LDLTS detects a change of the emission rate of the carriers from some, but not all, of the components of the broad peak when the LDLTS fill pulse length is changed. This change is ascribed to band edge modification as the electronic states associated with the dislocation charge up during the fill pulse, and causes local electric field-driven emission of trapped charge during the reverse bias phase of the measurement. The LDLTS features which remain constant with fill pulse are proposed to be due to point defects in the material, which are not physically near dislocations.