Evidence of valence band perturbations in GaAsN/GaAs(001): Combined variable-angle spectroscopic ellipsometry and modulated photoreflectance investigation

Abstract

The contribution of the fundamental gap E_ as well as those of the E_ + ∆ so and E + transitions to the dielectric function of GaAs 1-x N x alloys near the band edge were determined from variableangle spectroscopic ellipsometry and modulated photoreflectance spectroscopy analyses. The oscillator strength of the E_ optical transition increases weakly with nitrogen incorporation. The two experimental techniques independently reveal that not only the oscillator strength of the E + transition but also that of E_ + ∆ so become larger compared to that of the fundamental gap as the N content increases. Since the same conduction band is involved in both the E_ transition and its split-off replica, these results reveal that adding nitrogen in GaAs 1-x N x alloys affects not only the conduction but also the valence bands.

Application of photoreflectance to advanced multilayer structures for photovoltaics

“…In addition, the overview spectrum on the right panel shows PR-signatures attributed to the electronic structure of the nitride that have been identified according to the BAM as E -(1.2 eV), E -+Δ SO (1.54 eV), and E + (2.0 eV) in good agreement with previous results [27], although we cannot completely rule out subsidiary Franz-Keldysh oscillations (FKOs) affecting to some extent the apparent position of signatures above E 0 (GaAs). It should be mentioned that PR has significantly contributed to the development of the BAM, as described in the work of Walukiewicz and co-workers [23][24][25] and is one of the techniques routinely used for testing highly mismatched alloys.…”

Optical absorption of dilute nitride alloys using self-consistent Green’s function method

“…Perlin et al [5,6,22-24] measured the optical absorption spectra for In 0.04 Ga 0.96 N 0.01 As 0.99 and In 0.08 Ga 0.92 N 0.015 As 0.985 and compared them with GaAs absorption data. Turcotte et al [16,25] recently measured the optical absorption spectrum of GaN x As 1- x and In y Ga 1- y N x As 1- x for several values of x and y . Here, we calculate the absorption spectra for In 0.04 Ga 0.96 N 0.01 As 0.99 and compare them with Skierbiszewski measurements at different temperatures.…”

Effect of Sb in thick InGaAsSbN layers grown by liquid phase epitaxy

“…Nevertheless, this is an intriguing finding since a large refractive index of the alloys represents a significant advantage for the fabrication of high-performance optoelectronic devices [48]. The effect of Sb on the band structure of the alloy is largely limited on the valence band states, while N affects mainly conduction-band states; however the latter has been shown to also have a non-negligible effect on the valence band of the host material even in dilute concentrations [49]. Interactions between the valence band perturbations caused by N and Sb could represent one possible mechanism leading to changes in the refractive index and optical properties of the alloy; however further studies are needed in order to understand these effects.…”