Optical-absorption coefficient ofIn1−xGaxAs/InP

Optical-absorption coefficient data are presented over the 0.7–1.5-eV spectral range (825–1750 nm) for ${\mathrm{In}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ga}}_{\mathrm{x}}$As/InP; both at the lattice-matched condition x=0.47 and for the 0.45<x<0.51 composition range. Absorption data for such epilayers are compared at 10, 77, and 300 K. This comparison involves numerous epilayers grown by organometallic vapor-phase epitaxy, a lattice-matched layer grown by molecular-beam epitaxy, and published data for ${\mathrm{In}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ga}}_{\mathrm{x}}$As grown by liquid-phase epitaxy. It is demonstrated that these growth techniques yield material with equivalent absorption characteristics. For all compositions, the absorption coefficient α(hν) rises abruptly to near 6000 ${\mathrm{cm}}^{\mathrm{-}1}$ at the band gap, and increases more gradually to 30 000 ${\mathrm{cm}}^{\mathrm{-}1}$ at 1.5 eV. For energies above 1.3 eV, all the ${\mathrm{In}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ga}}_{\mathrm{x}}$As epilayers studied here show essentially the same absorption characteristics, regardless of composition or temperature.