Effect of irradiation by He⁺ and Ga⁺ ions on the 2D‐exciton susceptibility of InGaAs/GaAs quantum‐well structures

Abstract

The effect of irradiation by 30‐keV Ga+ and 35‐keV He+ ions (in relatively small doses) on the excitonic reflectivity spectra of single InGaAs/GaAs quantum‐well structures is studied. It is found that the irradiation results in decreasing intensity and broadening of the excitonic resonances in the reflectivity spectra for all the doses. It is shown that these changes are not related to a decrease of the exciton transition oscillator strength and, therefore, to the irradiation‐induced destruction of the excitonic states, but can be rather ascribed to a common cause, namely, to inhomogeneous broadening of the excitonic resonances proportional to the exposure dose. A tentative model of the irradiation‐induced broadening is considered, with the mechanism of the process being a consequence of scattering of the 2D excitons by structural defects associated with Ga(In) and As vacancies arising upon collisions of the high‐energy ions with regular atoms of the crystal structure. The model is used to compare experimental dependence of efficiency of the Ga+‐ion‐induced broadening on distance of the quantum well from the irradiated surface with a similar dependence calculated using the Monte‐Carlo technique. A discrepancy between the results of simulation and experimental data is discussed.

Modeling and optimization of the excitonic diffraction grating

“…Far from the resonance, the reflection coefficient behaves qualitatively as K 0 (∆ω) ∼ 1 ∆ω 2 , similarly to (11). The diffraction generated by the contrast of the spatial modulation decreases much faster: K 1 (∆ω) ∼ 1 ∆ω 4 .…”

“…Although modeling of the ion scattering for the case of 35 keV He + ions shows approximately the same vacancy generation yield for QW1 and QW2 [11], a direct comparison of the doses at which the maximum diffraction efficiency is observed does not allow us to make a conclusion about the ratio between coefficients β for these two QWs. However, if we assume that the proportionality coefficients between the inhomogeneous broadening and irradiation dose for QW1 and QW2 are close, then a lower optimal dose in the case of QW1 indicates a greater parasitic modulation, which is consistent with the wider scattering of ions in the sample at QW1 depth.…”

“…We will introduce average radiative widthΓ R = Γ R1 +Γ R2 2 . Reflection coefficient K 0 (∆ω) is described by (11) with the substitution Γ R →Γ R . Diffraction efficiency will be the following:…”

“…These dependencies reach a maximum at a certain dose. Previous studies have shown that ion-beam-induced inhomogeneous broadening is proportional to the irradiation dose [11]. This proportionality allows us to fit the data using developed theory assuming the presence of parasitic modulation of unirradiated grating grooves (denoted above by constant β).…”

Dynamical X‐ray diffraction theory: Characterization of defects and strains in as‐grown and ion‐implanted garnet structures

“…Another way to control the physical properties of garnets is the use of ion implantation for purposeful modifying the structure of crystal volume or subsurface layers . This effective technique provides, due to use of proper ion species and ion energies, the possibility to tailor the optical, magneto‐optical, magnetic, and electrical properties of multilayer semiconductor structures, magnetic films, etc.…”