CARRIER LIFETIMES IN SILICON

Carrier lifetimes in semiconductors are being rediscovered by the Si I C community, because the lifetime is a very effective parameter to cha racterize the purity of a material or device. It has become a process and equipment characterization parameter, The various recombination me chanisms are discussed and the concept of recombination and generation lifetime is presented, me show that surface recombination/generation plays an important role in today's high purity Si and will become yet more important as bulk impurity densities in Si are reduced further. F urthermore, the dependence of lifetime on impurity energy level and mi nority carrier injection level is discussed. Concepts are stressed in the paper, with the necessary equations to clarify these concepts, Whe rever possible, the concepts are augmented with experimental data, wit h particular emphasis on the case of iron in silicon, because Fe is on e of the most important impurities in Si today. We have used Si in the examples because lifetime measurements are most commonly made in Si.