Question 3 (40 points): The valence and conduction band structure of a hypothetical semiconductor are given respectively by E, (k) = B, cos(ka) and E.(k) = A, + B, cos(ka) , where A. =1leV, B. =4V, B =5eV, and a=5A. The dielectric constant of the semiconductor is 8 = 10. a) Plot the band structure. What is the value of the band gap? b) Is this a good light-emitting semiconductor? Explain why or why not. c) What are the values of the electron and hole effective masses at the conduction band minimum and valence band maximum, respectively? d) If donor atoms are added, what is the donor binding energy