Effects of external stress on defect complexes in semiconductors
Crystal field gradients that exist at lattice sites in solids depend on the symmetry of charge distribution around atomic sites. The charge symmetry could be broken either by the presence of impurity complexes in the host matrix or by external stress on the samples, which leads to an observable magnitude of electric field gradients (EFGs). The perturbed γ–γ angular correlation (PAC) method is employed here to investigate the effect of uniaxial stress on 111Cd sites in crystalline doped semiconductors.
STRESS AND TEMPERATURE DEPENDENCE OF THE HYPERFINE INTERACTIONS AT POINT DEFECTS IN SEMICONDUCTORS
The resultant electric field gradient (EFG) produced at the nucleus of an atom in a solid can be measured using the perturbed γ – γ angular correlation (PAC) method that employs radioactive probe atoms. Several EFGs, associated with different types of defects trapped by the probe, are reported from the crystal silicon and germanium semiconductors. However, the nature of the field gradients is not fully understood because of the many factors contributing for its properties. The proximity of an impurity atom to the probe in the host matrix particularly played a significant role in the determination of the magnitude of the EFG. We discuss here the temperature and stress dependence of the crystal EFGs caused by impurity trapping as well as by the actions of uniaxial stress on semiconductor substrates.
Pac studies of ion implanted silicon
The annealing behaviour of radiation induced defects in ion implanted silicon is studied by the perturbed angular correlation method (PAC). Between 700 K and 1000 K the trapping and detrapping of vacancy-oxygen complexes is observed. In annealed p-Si a well defined, axially symmetric electric field gradient (EFG) appears at low temperatures. This EFG is oriented to the surface and not to any crystallographic direction. The size of the EFG depends strongly on the surface charge.