Question: Defects in a semiconductor material introduce allowed energy states within the forbidden band gap. Assume that a particular defect in silicon introduces two discrete I ells: a donor level 0.25 eV above the top of the valence band, and an acceptor level 1 0.65 eV above the top of the valence band. The charge state of each defect is a function of the position of the Fermi level.
(a) Sketch the charge density of each defect the Fermi level moves from E, to E,. Which defect level dominates in heavily do d n-type material'? In heavily doped p-type material?
(b) Determine the electron and hole concentrations and the location of the Fermi level in
(i) an n-type sample doped at Na = 1017m-3 and
(ii) in a p-type sample doped at Nb = 1017m-3.
(c) Determine the Fermi level position if no do pant atoms is added. Is the material n-type, p-type, or intrinsic?