Deactivation In Heavily Arsenic-Doped Silicon

We have combined ab initio calculations with a general statistical theory to predict the properties of heavily arsenic-doped silicon. Although we find that a lattice vacancy surrounded by four arsenic (VAs4) is the dominant deactivating complex at high arsenic concentrations in equilibrium, vacancy clusters with fewer arsenic neighbors are present in significant quantities. These smaller complexes are essential not only to the establishment of equilibrium, since SiAs4 clusters are extremely rare, but can also explain deactivation even if VAs4 formation is kinetically inhibited. This suggests that materials with similar arsenic concentration and deactivation fractions can have different microscopic states, and therefore behave differently in subsequent processing. Good agreement is found between theory and experiment for the electronic concentration as a function of temperature and total arsenic concentration. We also show that for low arsenic concentrations, full activation is the equilibrium condition. (C) 1998 American Institute of Physics.