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Ch.12 - Solids and Modern Materials
Chapter 12, Problem 79

GaAs and GaP make solid solutions that have the same crystal structure as the parent materials, with As and P randomly distributed throughout the crystal. GaPxAs1 - x exists for any value of x. If we assume that the band gap varies linearly with composition between x = 0 and x = 1, estimate the band gap for GaP0.5As0.5. (GaAs and GaP band gaps are 1.43 eV and 2.26 eV, respectively.) What wavelength of light does this correspond to?

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1
Identify the given band gaps for GaAs and GaP: GaAs has a band gap of 1.43 eV and GaP has a band gap of 2.26 eV.
Recognize that the problem states the band gap varies linearly with composition. This means we can use a linear interpolation formula to find the band gap for GaP_{0.5}As_{0.5}.
Apply the linear interpolation formula: E_{gap}(GaP_{0.5}As_{0.5}) = (1-x) * E_{gap}(GaAs) + x * E_{gap}(GaP), where x = 0.5.
Substitute the known values into the formula: E_{gap}(GaP_{0.5}As_{0.5}) = (1-0.5) * 1.43 eV + 0.5 * 2.26 eV.
To find the corresponding wavelength of light, use the equation \( \lambda = \frac{hc}{E} \), where \( h \) is Planck's constant, \( c \) is the speed of light, and \( E \) is the energy in electron volts.