Piezoreflectance and contactless electroreflectance spectra of an optoelectronic material: GaInNP grown on GaAs substrates

Abstract

We report a detailed study of piezoreflectance (PzR) and contactless electroreflectance (CER) on Ga 0.44In 0.56N x P 1− x epitaxial layers at room temperature. The polarized PzR spectra show anisotropic character along the [1 1 0] and [1 1 ̄ 0] directions. Ordering-induced superlattice-like microstructure shown in high resolution transmission electron microscope (HTEM) images confirms the spontaneous ordering in Ga 0.44In 0.56N x P 1− x epitaxial layers. The obtained PzR and CER spectra are fitted with the theoretical line shape functional form. The valence-band maximum, crystal field/strain splitting and spin–orbit splitting to conduction band transition energies denoted as E g, E g+Δ 12 and E g+Δ 13, respectively, are accurately determined. With nitrogen incorporation, the PzR and CER features red-shifts, indicating band gap reduction. The experimentally observed band gap energy reduction of GaInP incorporation nitrogen is of the same order as for nitrogen in binaries. However, the bowing coefficient b is determined to be −10.5 eV, that is considerable smaller than that of the incorporation of nitrogen in InP ( b=−16 eV) or GaP ( b=−14 eV).