3.091 Fall Term 2004 Homework Quiz #5Bsolution outline (a) Green light, λ= 518 nm, shines on a crystal of gallium arsenide (GaAs), which has a band gap energy, Eg, of 1.34 eV. Is GaAs transparent to green light? Justify your answer with appropriate calculations. To determine whether GaAs is transparent to green light, compare the incident photon energy to the value of the band gap energy. If Eincident> Eg, then electrons will be promoted across the band gap thereby absorbing the incident radiation. 3481996.63 103.00 103.84 10J2.40eV518 10incidenthcEλ−−−×××===× =×Clearly, Eincident
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