Determine the output wavelength of a GaAs1-xPx material for two different mole fractions. Consider first GaAs and then GaAs1-xPx.

Question

Determine the output wavelength of a [latex]\mathrm{GaAs}_{1-x} \mathrm{P}_{x}[/latex] material for two different mole fractions.

Consider first GaAs and then [latex]\mathrm{GaAs}_{1-x} \mathrm{P}_{x}[/latex].

Accepted Answer

GaAs has a bandgap energy of [latex]E_{g}=1.42 \mathrm{eV}[/latex]. This material would produce a photon output at a wavelength of

[latex]\lambda=\frac{1.24}{E}=\frac{1.24}{1.42}=0.873 \mu \mathrm{m}[/latex]

This wavelength is in the infrared range and not in the visible range. If we desire a visible output with a wavelength of [latex]\lambda=0.653 \mu \mathrm{m}[/latex], for example, the bandgap energy would have to be

[latex]E=\frac{1.24}{\lambda}=\frac{1.24}{0.653}=1.90 \mathrm{eV}[/latex]

This bandgap energy would correspond to a mole fraction of approximately [latex]x=0.4[/latex].

Comment

By changing the mole fraction in the [latex]\mathrm{GaAs}_{1-x} \mathrm{P}_{x}[/latex] system, the output can change from the infrared to the red spectrum.

Question 14.7: Determine the output wavelength of a GaAs1-xPx material for ...

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