Past exam of the condensed matter physics course of the University of Oxford 2017 4 d i Solution 2026-10-25
At , . With the scalar effective masses and two-spin convention of a, the effective density of states values areThe intrinsic carrier concentration follows from :From b, . Taking as a reference,It lies above the middle of the band gap, because the hole effective density of states is larger. Both band edges are more than twenty away, validating the nondegenerate semiconductor approximation.