Problem 5 a) Show that green light (λ = 5 x 10-7 m) can excite electrons...

Problem 5

a) Show that green light (λ = 5 x 10-7 m) can excite electrons across the band gap of silicon (Si).

b) i. Electromagnetic radiation of frequency 3.091 x 1014 Hz illuminates a crystal of germanium (Ge). Calculate the wavelength photoemission generated by this interaction. Germanium is an elemental semiconductor with a band gap, Eg, of 0.7 eV. ii. Sketch the absorption spectrum of germanium, i.e., plot % absorption vs. wavelength, λ.

c) Potassium (K) and beryllium (Be) are metals which exhibit good electrical conductivity. Explain for both elements the reasons for the observed conductivity on the basis of the band structure.

d) A pure crystalline material (no impurities or dopants are present) appears red in transmitted light. i. Is this material a conductor, semiconductor or insulator? Give the reasons for your answer . ii. What is the approximate band gap (Eg) for this material in eV?

e) An unknown material is transparent to light of frequencies ( ν ) up to 1.3 x 1014 s–1 . Draw a meaningful schematic band structure for this material.

Expert Solution

genius_generous answered 2 years ago

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