Franz-Keldysh oscillations in photoreflectance spectra of complex AlxGa1?xAs structures

Abstract

Room temperature photoreflectance spectroscopy (PR) was used to investigate MBE grown AlxGa1−xAs/GaAs doped structures. For some structures photoreflectance spectra exhibit superposition of Franz – Keldysh oscillations. Using the 632.8 nm line from an He – Ne laser and the 457.9 nm line from an Ar+ laser alternately as the pump light, the Franz – Keldysh oscillations from different interfaces were separated. From the period of the oscillations, the built-in electric field at two interfaces was determined. The dependence of the direct band-gap energy on the Al content was also investigated. To obtain the direct band gap energy, the measured photoreflectance spectra were analysed using Aspnes lineshape procedure. The determined EAlGaAs dependence on x for doped AlxGa1−xAs layers was compared with previous data. Copyright © 2000 John Wiley & Sons, Ltd.