Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures

Abstract

The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga1 − xInxNyAs1 − y/GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated.

Nitrogen induced localised-state ensemble effect on multi quantum well GaInNAs with low indium concentration

“…It illustrates that the E − is 1.152 eV and 1.142 eV for sample A and B, respectively. The change of E − was 10 meV per 0.1% N, which correlates with eports by Sarcan et al [37] and Erol et al [38], that stated the increment of 100 meV per 1% of N composition, and in the low range in the effect of N fraction on the energy band gap of GaInNAs [39,40]. The BAC results correspond to the experimental PL redshift emission at 300 K, as depicted in figure 1(b), which also demonstrates low optical quality and broader full width at half maximum (FWHM) with increasing N fraction.…”

A study on the voltage-dependent response of a GaInNAs-based pin photodetector with a quasi-cavity

“…The quasi-cavity resonance and PL peak wavelength of the photodetector are observed at 1286 nm. In the literature, the FWHM of the PL spectrum of a GaInNAs (N>1.5%, In ~32%) alloy is about 60-80 nm, depending on the elemental compositions [14]. In our measurements, the FWHM of the PL spectrum is narrowed as an effect of the presence of the quasi-cavity and the FWHM is an appropriate width of an optical communication window centred at 1.3 μm.…”

Influence of TiO2 and Si on the exciton–phonon interaction in PbI2 and CdS semiconductors evidenced by Raman spectroscopy

“…The modification in relative intensities of the principal peaks of graphene and graphite has extensively studied in order to reflect the evolution of the exciton-phonon interaction [37]. Based on this behavior, the influence of TiO 2 and Si on the exciton-phonon interaction strength, which is assessed in figures 5(b) and 7(a), is explained by the differences between the relative intensities of the Raman line of PbI 2 peaked at 97 cm ) indicates transferred electrons with a higher kinetic energy from PbI 2 , which induce more electron-phonon scattering events during their relaxations [34]. Therefore, a stronger exciton-phonon interaction is observed in the PbI 2 /TiO 2 mixture, whereas the excitonic PL of PbI 2 is predominantly quenched in the PbI 2 /Si mixture, leading mostly to a decrease of the SRS effect evidenced by the decrease in intensity of the vibrational mode of PbI 2 peaked at 97 cm −1 .…”

“…As in the case of TiO 2 , in the Si semiconductor the electrons are expected to migrate rapidly to the energetic levels of the CB of Si, decreasing the probability of mixing of the two optical fields in a nonlinear process for the line peaked at 97 cm −1 . Since the excitation laser energy is much higher than the band gap energy of Si (1.9 eV), the electrons are excited to higher states in the CB of Si and the excess of energy is usually dissipated due to carrier relaxation to their respective band edges via multiple phonon scattering [34]. Therefore, because of the energy transfer from the PbI 2 towards the Si, the intensity of the Raman mode of Si in the PbI 2 /Si mixture is enhanced at low-temperature (red curve) due to the charge transfer mechanism that induces strong exciton-phonon coupling when the incident laser light and the excitonic PL of PbI 2 induce a nonlinear optical process in Si.…”