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What are direct and indirect band gap semiconductors???

Answer»

For the direct band gap MATERIAL, you have to plot (αhv)2 vs. hv (ENERGY in eV). Where, α is ABSORPTION coefficient (cm-1), hv is energy in eV. Then, the direct band gap energy, Eg, can be obtained by extrapolating the linear portion to (αhv)2 = 0 in that GRAPH. For the INDIRECT band gap material, you have to plot (αhv)1/2 vs. hv (energy in eV). Where, α is absorption coefficient (cm-1), hv is energy in eV. Then, the indirect band gap energy, Eg, can be obtained by extrapolating the linear portion to (αhv)1/2 = 0 in that graph.



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