Differential Electroabsorption

Electroabsorption Spectroscopy Measurements of the Exciton Binding Energy, Electron–Hole Reduced Effective Mass, and Band Gap in the Perovskite CH3NH3PbI3

“…It is well known that modulation spectroscopic techniques provide extremely sharp spectra of individual critical point (CP) absorption features in semiconductors due to the elimination of effects such as optical scattering and background absorption from broad neighboring critical point features that appear in techniques such as ellipsometry or transmission/reflection spectroscopy. For this reason, modulation spectroscopy is often considered a superior technique for the determination of band edge properties in semiconductors. , Electric-field modulation spectroscopy is highly sensitive to Coulomb correlation effects of Wannier excitons, which makes it an interesting technique for studying exciton effects at critical points. − Here we use electroabsorption (EA) spectroscopy to provide sharp, derivative-like fundamental absorption edge spectra of CH 3 NH 3 PbI 3 at 300 K and reduced temperature. We find that the EA spectra at room temperature are represented by a form of the one-electron Franz–Keldysh–Aspnes (FKA) low-field theory − as opposed to the quadratic Stark effect, − which explains the third-derivative-like χ (3) EA response measured in our experiment.…”

The Franz–Keldysh effect revisited: Electroabsorption including interband coupling and excitonic effects

“…Our results are slightly different from previous two-band model calculations with Coulomb interaction that consider the contributions from the hydrogenic exciton wavefunctions only at the origin. [21][22][23] In our scheme this would require fixing the dipole moment matrix element to the value at The inset shows the energy range from 1.6 to 1.9 eV in more detail.…”

“…The Fourier transform of the optical pulse, E opt (ω), is defined similarly to Eq. (22). Since the interband polarization is linear in the optical field we can writē…”

“…The Coulomb interaction, however, modifies significantly the optical properties due to the formation of correlated electron-hole pairs, and needs to be included. Initial efforts to add these excitonic effects, both numerically and semianalytically, were made within the effective mass approximation; [19][20][21][22][23][24] this simple approximation is still used to analyze experimental data. 25 Rees provided a more complete method to compare theory and experiment, 26,27 including not only the electron-hole interaction but also lattice defects, band anisotropy, lifetime broadening and surface effects.…”

Инфракрасное Фотоотражение Полупроводниковых Материалов a-=sup=-3-=/Sup=-B-=sup=-5-=/Sup=- ( О Б З О Р )

“…5). Как было предсказано в [42], экситонные эффекты несколько увеличивают период осцилляций по сравнению с результатами одноэлектронной теории. Это хорошо видно из оценок i , сделанных значительно позднее в [34].…”