Interference Effect on the Phase of Franz–Keldysh Oscillations in GaAs/AlGaAs Heterostructures

Abstract

We have studied photoreflectance spectra of GaAs/Al 0:3 Ga 0:7 As heterostructures from the viewpoint of the phase of Franz-Keldysh (FK) oscillations. The phase of the FK oscillations originating from the GaAs buffer layer shifts with the change of the Al 0:3 Ga 0:7 As-layer thickness, while the period does not vary. The FK-oscillation phase does not depend on the pump power, which suggests that the phase shift is not caused by a difference in the magnitude of modulation. We propose a calculation model for FK oscillations that includes the interference of probe light. Photoreflectance spectra calculated on the basis of this model are compared with the measured spectra. We conclude that mixing of the real and imaginary parts of a modulated dielectric function, which is caused by the probe-light interference, gives rise to the phase shift of the FK oscillations. We also derive a novel analysis method for a linear plot of the extremum positions of FK oscillations based on the above line-shape model. The present method remarkably reduces ambiguity in the estimation of band-gap energy that is considerable in a conventional analysis.

Photovoltaic effects on Franz–Keldysh oscillations in photoreflectance spectra: Application to determination of surface Fermi level and surface recombination velocity in undoped GaAs∕n-type GaAs epitaxial layer structures

“…In order to analyze the phase shift, we generalize the line-shape function of the FKOs. As previously reported, 15,16 the presence of the overlayer causes the interference of the probe beam, which leads to the phase shift of the FKOs. Next, we calculate the line shape of the FKOs using Eqs.…”

“…Furthermore, we also discuss the line shape of the FKOs from the as-grown i-GaAs/ n-GaAs structure, especially focusing on the phase factor. As previously reported, 15,16 the analysis of the phase of FKOs is useful to reduce ambiguity in estimating the electric-field strength. However, the line shape of the FKOs from the i-GaAs/ n-GaAs structure has not been discussed in detail though such a structure has been employed in many studies.…”

Photoreflectance and surface photovoltage spectroscopy of beryllium-doped GaAs∕AlAs multiple quantum wells

“…23 In addition, the phase of FKOs originating from the buried interface shifts strongly with the change of the epilayer thickness due to an interference effect. 24 We therefore used these peculiarities of the spectra to disclose the origin of FKOs. Let us consider in more detail the PR results for samples 1807, 1794, and 1795 given in Fig.…”

Photoreflectance study of GaAsSb∕InP heterostructures

“…No significant effect is detected on the electric field value. Next, we a priori assume that phase does not depend a lot on the temperature, following previous studies 4 which have shown that it essentially depends on optical interferences, which hardly depend on temperature.…”

“…Photoreflectance ͑PR͒ spectroscopy has been used to characterize semiconductor heterostructures and a number of device structures such as heterojunction bipolar transistors ͑HBT͒, [1][2][3][4] high electron mobility transistors, 5,6 and quantum well lasers. 7 Because of its derivative-like nature a large number of sharp spectral features can be observed, even at room temperature, and it is possible to determine the energy and broadening parameter of any direct interband transition.…”