Absorption and electroabsorption spectra of an In1−xGaxP1−yAsy/InP double heterostructure

Abstract

Electroabsorption spectra of an InGaAsP/InP double heterostructure are compared with absorption and luminescence spectra. The alloy tuned to emission at 1.33 μm at room temperature shows a surprisingly narrow spectrum at the fundamental gap with many Franz–Keldysh oscillations. The analysis of the electroabsorption data yields the energy gap, its dependence on temperature, and the spin-orbit splitting. Line shape analysis provides information on lifetime broadening, on internal fields, and space charges, and reveals the presence of excitonic effects. Although discrete exciton levels were not observed, an exciton binding energy of 2.3 meV is obtained from the continuum states which is consistent with a reduced effective mass of 0.03m0. While absorption and electroabsorption data yield the same value of the energy gap, emission of light at low temperature occurs at significantly lower energies pointing to the presence of tail states below the gap.