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EE335_11-HW03 - 2(10 Refer to problem 3 in HW I If each...

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EE 335001 Homework III Fall 2011 Due: Thursday, Oct. 06, 2011 1. (10%)(a) It was mentioned in Section 3.2 that the covalent bonding model gives false impression of the localization of carriers. As an illustration, calculate the radius of the electron orbit around the donor in Fig. 3-12c, assuming a ground state hydrogen-like orbit in Si. Compare with the Si lattice constant. Use m n * = 0.26 m o for Si. (10%)(b) Repeat part (a) for the radius of an electron orbiting around the donor in GaAs, assuming m n * = 0.067 m o for GaAs. Compare the radius with the GaAs lattice constant. (10%)(c) Refer to part (a) and estimate the donor binding energy for Si. Compare your results to the donor levels of simple donors such as P, As and Sb as shown in Fig. 4-9 (page 119).
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Unformatted text preview: 2.(10%) Refer to problem 3 in HW I. If each gold atom donates one electron to the gold matrix at room temperature, estimate the electron concentration of gold. Is gold a conductor? 3. (10%)In practice we assume that the intrinsic Fermi level, Ei, coincides with the center of the band gap. In reality it is not true. Derive an expression relating the intrinsic level Ei to the center of the band gap. Find the displacement of Ei from the center of the band gap for both silicon and germanium at room temperature. The effective mass values are m n * = 0.55 m o for Ge and 1.1 m o for Si, m p * = 0.37 m o for Ge and 0.56m o for Si where m o is the free electron mass....
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