Conduction band structure of GaInP

The intrinsic absorption edge of ${\mathrm{Ga}}_x{\mathrm{In}}_{1-x}\mathrm{P}$ alloys has been investigated by piezomodulation spectroscopy between helium and room temperature. The comparison of modulated reflectivity and transmission spectra gives clear evidence of the participation of $L$ and $X$ conduction minima to the indirect process. At 10°K, direct determination of the ${\Gamma }_{1c}-L_{1c}$ and $X_{1c}-L_{1c}$ crossover compositions ($x_c=0.68\mathrm{}$ and $x_c=0.77\mathrm{}$, respectively) permits one to resolve the discrepancies existing in the literature on this alloy. The contribution of resonant indirect transitions to $\Delta {\epsilon }_1$ is observed for the first time.