Ion-beam-assisted spatial modulation of inhomogeneous broadening of a quantum well resonance: excitonic diffraction grating

Abstract

We propose a method of spatial modulation of inhomogeneous broadening of a quantum-well excitonic resonance based on local generation of defects produced by a focused ion beam. The method is applied to fabrication of excitonic diffraction grating in a single quantum-well InGaAs/GaAs structure by irradiating the sample with a beam of 35-keV He⁺ ions of exposure doses <10¹² cm^-2. The spectrum of resonant diffraction on such a structure is narrower than that of reflectivity and decreases much faster with increasing temperature. A proposed model of formation of the diffractive response based on the single scattering approximation well describes the results of the spectral and temperature measurements.

Modeling and optimization of the excitonic diffraction grating

“…In this work we present a theoretical modeling of the excitonic diffraction grating by the step-by-step approximation of the Maxwell equation solution. This model, being applicable for large Γ R Γ N R , makes it possible to correctly describe experimental data presented in [12], as well as in our earlier work [17], where resonant diffraction was observed from the QW grown on the substrate, pre-patterned by the ion beam irradiation. Developed model was also used to show the way to the further increase of the diffraction efficiency, and to predict resonant diffraction spectra in the case of the spatial modulation of the excitonic resonance radiative width or spectral position.…”

“…For a theoretical description of this phenomenon in [12] we used the single scattering model. This model allowed us to obtain a qualitative description of the reflection and diffraction spectra.…”

“…However, this model is applicable only in the case of the radiative width of the excitonic resonance Γ R being much smaller than the non-radiative broadening Γ N R . For QW used in [12] Γ R Γ N R ≈ 0.3. For higher quality molecular beam epitaxy grown QWs this ratio could reach 0.45 for GaAs/Al 0.3 Ga 0.7 As QWs [13], 0.6 for GaAs/Al 0.03 Ga 0.97 As QWs [14].…”

“…In [12] we have utilized the post-molecular-beam-epitaxy (MBE) growth ion beam irradiation for spatial modulation of the inhomogeneous broadening of the exciton resonance in QW. Periodical spatial modulation lead to the formation of a new coherent response -resonant diffraction.…”

A review of defect engineering, ion implantation, and nanofabrication using the helium ion microscope

“…The HIM has also been used to tune the optical properties of quantum well structures [ 61 ]. In this work, epitaxially grown InGaAs/GaAs single quantum well structures were patterned with sets of stripes to emulate a grating structure, using doses of less than 10 12 ions/cm 2 .…”