We have performed a detailed contactless electroreflectance study of the interband excitonic transitions on both the Ga and N faces of a 200-m-thick freestanding hydride-vapor-phase-epitaxy grown wurtzite GaN sample with low defect concentration in the temperature range between 20 and 300 K. The transition energies of the A, B, and C excitons and broadening parameters of the A and B excitons have been determined by least-square fits to the first derivative of a Lorentzian line shape. The energy positions and separations of the excitonic transitions in the sample reveal the existence of residual strain. At 20 K the broadening parameter of A exciton deduced for the Ga (5ϫ10 5 dislocation cm Ϫ2) and N (1ϫ10 7 dislocation cm Ϫ2) faces are 3 and 7 meV, respectively, indicating a lower defect concentration on the former face. The parameters that describe the temperature dependence of the interband transition energies of the A, B, and C excitons as well as the broadening function of the A and B features are evaluated. The results from an analysis of the temperature dependence of the broadening function of excitons A and B indicate that GaN exhibits a very large exciton-phonon coupling.

Electroreflectance spectroscopy has been used to study a GaAs/Ga0.77Al0.23As symmetrically coupled double quantum well system as a function of externally applied electric field. Both intra- and inter-well exciton transitions were detected. The energy shifts of the coupled quantum confined levels are in good agreement with a theoretical calculation. Details of the lineshape fit yield important information about the modulation mechanism.

Temperature dependent surface photovoltage spectra of type I GaAs1−xSbx/GaAs multiple quantum well structures J. Appl. Phys. 113, 073702 (2013); 10.1063/1.4792065 Photoreflectance and surface photovoltage spectroscopy of beryllium-doped Ga As ∕ Al As multiple quantum wells J. Appl. Phys. 98, 023508 (2005); 10.1063/1.1978970 Temperature dependent photoreflectance and photoluminescence characterization of GaInNAs ∕ GaAs single quantum well structures J. Appl. Phys. 96, 6298 (2004); 10.1063/1.1805724Modeling and analysis of photomodulated reflectance and double crystal x-ray diffraction measurements of tensilely strained InGaAs/InGaAsP quantum well structuresWe present photoreflectance ͑PR͒ and surface photovoltage spectroscopy ͑SPS͒ studies of GaAs 1−x Sb x / GaAs multiple quantum well structures with fundamental transition close to 1.3 m. These two optical diagnostic tools are powerful supplementary techniques in the investigations of complicated quantum systems. PR gives detailed information about the heavy-holes related transitions, while SPS contains additional information concerning light-holes related ones. The comparison of experimental data and theoretical analysis based on the envelope function approximation, including strain and exciton binding energy, allows us to identify the observed PR and SPS features. The results point to the existence of weak type-I band alignment in samples being studied, and the Sb content dependent of conduction band offset is found to agree well with that reported by Wang et al. ͓Phys. Rev. B 70, 195339 ͑2004͔͒.