The Properties of Iron in Silicon

Abstract

The properties of iron in n‐type and p‐type silicon were studied by means of DLTS, carrier lifetime measurements, and infrared absorption spectroscopy. Only one donor level was observed, situated at and correlated to iron on an interstitial site. In p‐Si:B iron‐boron pairs were formed at room temperature. Their activation energy was determined to be . The reaction proceeded in two phases. In the second phase a thermal equilibrium between iron and iron‐boron pairs was found which could be shifted by annealing and illuminating the specimen, respectively. In aluminum‐doped silicon crystals two levels were observed after iron diffusion correlated to iron‐aluminum pairs. Their activation energies were determined to be . It is assumed that iron‐boron pairs form also two levels, a donor and an acceptor. The acceptor must be situated in the upper half of the silicon bandgap. Reaction mechanisms are discussed.