A study of Franz–Keldysh oscillations in the photo reflectance spectrum of the δ-doped GaAs film

Abstract

Very high carbon δdoping concentration in Al x Ga1−x As grown by metalorganic vapor phase epitaxy using trimethylaluminum as a doping precursor Our photo reflectance ͑PR͒ spectroscopy measurements of the ␦-doped GaAs film at 300 K reveal many Franz-Keldysh oscillations ͑FKOs͒ above the valence band edge, E 0 and the spin-orbit split energy, E 0 ϩ⌬ 0 , which enables us to determine the electric field strength from periods of FKOs provided reduced masses of the electron and holes are known. The reduced masses can be determined unambiguously at E 0 ϩ⌬ 0 , but not at E 0 , at which the heavy-and light-hole transitions are degenerate. However, the ambiguity at E 0 can be resolved by applying the fast Fourier transform to the PR spectrum to separate the contributions from the heavy and light holes.

Optical characterization of GaInP p–i–n solar cells

“…The inset in Fig. 1 shows a plot of ðE j À E g Þ 3=2 vs j, which yields a straight line with a slope proportional to F. 28) Figure 2 shows the ER spectra of sample A measured at different reverse biases between 0 and 3.5 V. The first feature below 1.88 eV shows the direct energy band gap (E g ) of the i-layer, whereas features above 1.88 eV are the FKO features. The photon energies of FKO extrema (local maximums and minimums), which are labeled 1-5 and indicated by lines with arrows in the end, increase with increasing reverse bias owing to the increase in the built-in electric field.…”

Photoreflectance study of the GaAs buffer layer in InAs/GaAs quantum dots

“…The optical properties of InAs/GaAs QDs have been investigated via photoluminescence (PL) and photoluminescence excited (PLE) techniques [20][21][22], but the information obtained is often limited to only the lower energy states, which does not allow a deduction of the shape of QD potential. However, other methods, such as electroreflectance (ER) [23][24][25], reflectance-difference [26] and photoreflectance (PR) [16,[23][24][27][28] techniques can detect higher energy transitions in the QD and other layers.…”

“…It is known that PR spectra can be classified depending on the electric field strength in depletion region [24,28], and thus, the appearance of FKOs in the PR spectrum indicates medium field regimen. These spectra were fitted by using a damped FKO above the gap originating from the epitaxial GaAs surface.…”