Luminescence anomaly in band gap tailored In0.53(GaxAl1-x)0.147As quaternary alloy grown by molecular beam epitaxy

Abstract

In0.53(GaxAl1-x)0.47As epilayers with band gap energy varying from 0.78 to 1.42 eV are grown lattice matched to InP substrate by MBE technique. The lattice mismatch and crystalline quality of the layers are assessed by the double crystal X-ray diffraction and the lattice vibrations due to the three binary compounds in the alloy are observed in the Raman spectra. Photoluminescence studies in the range 4-100 K showed an anomalous "inverted S" shaped variation in the PL energy versus temperature plot for epilayers with Al mole fraction less than 0.2. For mole fraction greater than 0.2, the characteristic dip in the energy values disappears and the normal band gap energy versus temperature relation is restored. Strong localization of excitons is associated with such a behavior in Al rich InGaAlAs epilayers.