Effect of random well-width fluctuations on the exciton optical absorption spectrum in single quantum wells

Abstract

The optical density function is calculated in a single quantum well for two-dimensional excitons moving in a random potential in the interfacial plane generated by fluctuations of the quantum-well thickness. Assuming Gaussian statistics for the random potential distribution, we have applied the path-integral approach and obtained in the adiabatic approximation two asymptotic analytical expressions for the low-and high-energy tails of the optical absorption spectrum. The high-energy tail of the exciton absorption line is also calculated using the perturbation theory. In order to obtain the spectrum across the whole energy range an analytical interpolation formula is found between the asymptotic expressions in the two cases, taking into account the proper normalization of the spectral function. The calculated optical density function is asymmetrically broadened, the magnitude of the peak is reduced, and the maximum is shifted to lower energy in both cases considered, as the disorder increases, in agreement with other theoretical results. Using the fitting parameters to the time-resolved photoluminescence data of Zimmermann ͓Nuovo Cimento D 17, 1801 ͑1995͔͒, we find that the path-integral method leads to results for the spectral widths ͑full widths at half maximum͒ that are closer to those experimentally observable, as compared with results inferred from the perturbation theory approach. This can be attributed to the additional contribution of the localized exciton states from the Kane band tail in the former method. The effect of varying the correlation length ͑at a fixed depth of the random potential fluctuations͒ on the optical density function is also studied.

Optical properties of homo- and heteroepitaxial single quantum wells grown by pulsed-laser deposition

“…As known from other groups [32,33], using a comparable approach to describe the interface roughness of quantum wells, one has to distinguish between islands larger than the exciton Bohr radius, separated by monolayer steps, and much smaller areas with a certain microroughness, so that the exciton rather sees rapid fluctuations than monolayer steps of c=2 [34]. In the first case we would expect a splitting of the exciton luminescence.…”

Disorder effect on intersubband optical absorption of n-type δ-doped quantum well in GaAs

“…With these in mind, it is clear that the absorption properties in low dimensional system are strongly influenced by disorder [33,34,39,[43][44][45][47][48][49]. For instance, Burresi and collaborators [42] provide experimental evidence that 2D disordered photonic architecture applied to a thin film material induces an enhancement in the absorption of the thinfilm solar cells.…”

“…Bansal et al [34] reported that the interface disorder of AlGaAs/GaAs quantum wells at high magnetic field reduces inhomogeneously broadened photoluminescence linewidth. Sa-yakanit et al [49] reported that the random potential generated by the fluctuations of the quantum-well thickness Al x Ga 1−x As/GaAs/ Al x Ga 1−x As exhibits a monotonic broadening and decrease of the magnitude of the exciton absorption peak with increasing disorder. Other examples in the literature on the effect of disorder on absorption, Banon et al [39] presented a mathematical and computational model able to simulate the optoelectronic response of semiconductor alloys with a compositional disorder.…”