513.001 Molecular and Solid State Physics

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Effective mass - Exam 24 February 2009

In a semiconductor where the bottom of the conduction band is at k = 0, an electron moves with a wavenumber k = 1010 m-1.

(a) If the effective mass of electrons in the conduction band is 0.5 m, what is the energy of this electron measured from the bottom of the conduction band?

(b) Electrons in the conduction band will occupy some states up until about kBT above the bottom of the conduction band. What is the maximum value of k that electrons would have from thermal fluctuations at room temperature? What consequences does this have for a light emitting diode?