Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

Room temperature absorption spectra of low temperature molecular beam epitaxy grown GaAs (LT‐GaAs) and AlGaAs (LT‐AlGaAs) are reported. We performed measurements in an extended spectral range from 0.8 eV to photon energies of 2.8 eV far above the band gap. For as‐grown LT‐materials, the absorption coefficients at the band gap are twice as high as for high temperature grown materials. By annealing the samples, we obtained a drastic reduced absorption coefficient below as well as above the band gap. We observed absorption changes up to 17 000 cm−1 for LT‐GaAs and 9000 cm−1 for LT‐AlGaAs taking place in a two phase process.