Hall mobility drops in disordered boron-doped Czochralski silicon compensated by thermal donors activation

We investigated the variation of majority carrier Hall mobility in Boron-doped Electronic-Grade Silicon progressively compensated by Double Thermal Donors. We show a strong reduction in Hall mobility around full compensation in both p- and n-type Si. We relate this drop in mobility to a rising inhomogeneity of the electrostatic potential associated with increasing compensation, as revealed by minority carrier diffusion length mapping. Two consequences of this inhomogeneity are considered to explain our data: 1) a physical scattering of carriers by submicronic non-uniformity of the electrostatic potential and 2) a bias in the determination of the Hall mobility in highly compensated Si. We show that the Hall Effect is indeed affected at high compensation level by the large-scale inhomogeneity in carrier density related to non-uniform dopant distributions. In parallel, we also discuss the possible existence of microscopic variations in dopants distribution that could lead to physical reductions in mobility. We eventually suggest suitable experiments that could reveal them. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)