Master thesis presentation Alexandru Golic, MPPHS

Abstract:

It has long been known that the density of states in a semiconductor near the edge of a band decays exponentially into the gap. This tail in the density of states is caused by impurities in the atomic lattice, creating localized states in the gap region. By modeling the impurities as a correlated Gaussian noise, it is possible to utilize path integrals to calculate the density of states in the tails. In this thesis I examine how the shape of the band affects the band tail when compared to a quadratic dispersion |k|^2. I find that for monomial dispersions |k|^q the tails do not differ qualitatively from a quadratic dispersion, but I find a difference for polynomial dispersion relations with multiple wells.

Supervisor: Johannes Hofmann
Examiner: Ulf Gran
Opponent: Emil Ingelsten