Ultrashallow p +-n junctions in silicon (100): Electron-beam diagnostics of the surface zone

Abstract

Ultrashallow p +-n junctions formed in silicon (100) under nonequilibrium impurity diffusion conditions are analyzed by electron-beam diagnostics of the surface zone using a probe of low-to medium-energy electrons. The energy dependence of the radiation conductivity is investigated, along with its distribution over the area of the p +-n junction. This procedure can be used to determine the depth distribution (in the crystal) of the probability of separation of electron-hole pairs by the field of the p-n junction; the experimental results show that this distribution differs according to whether the kick-out mechanism or the dissociative vacancy mechanism of impurity diffusion is predominant as the basis of formation of the ultrashallow p +-n junctions. Also reported here for the first time are the results of investigations of the distribution of secondary point centers formed near the boundary of the ultrashallow diffusion profile, which exert a major influence on the transport of nonequilibrium carriers. The data obtained in the study demonstrate the possibility of improving the efficiency of photodetectors, α-particle detectors, and solar batteries constructed on the basis of ultrashallow p-n junctions.