Raman and AFM studies of swift heavy ion irradiated InGaAs/GaAs heterostructures

Abstract

The effect of swift heavy ion (SHI) irradiation on InGaAs/GaAs heterostructures is studied using Raman spectroscopy and atomic force microscopy (AFM). The structures consist of molecular beam epitaxy (MBE) grown InGaAs layers on GaAs(001), having layer thicknesses of 12, 36, 60 and 96 nm. After irradiation, the GaAs type longitudinal optical (LO) mode blue shifted to higher frequency in thin samples and red shifted towards lower frequency in thick samples. These results are discussed invoking the penetration depth of the probe radiation (λ = 514.5 nm) in InGaAs. Deconvoluting the Raman spectra of thin samples indicates a compressive strain developed in the substrate, close to the interface upon irradiation. This modification and diffusion of indium across the interface results in an increase of strain and reduction of the defect densities in the InGaAs layer. The variations in FWHM of the Raman modes are discussed in detail. The surface morphology of these heterostructures has been studied by AFM before and after SHI irradiation. These studies, combined with Raman results, help to identify different relaxation regimes.

Surface‐interface analysis of InxGa1‐xAs/InP heterostructure in positive and negative mismatch system

“…The relationship between the shift of GaAs‐like LO frequency and the stress in the epitaxial layer can be expressed as follows: where F is the residual stress ( F is tensile stress at this time), ωLO 0 is the frequency of epitaxial In x Ga 1‐x As without stress, Ω LO is the measured GaA...…”

Micro-Raman for compositions characterization of selective area growth of AlxGayIn1−x−yAs materials by metal-organic vapor-phase epitaxy

“…The backscattering z(-,-)z configuration was used to analyze the Raman spectra, where z ¼ /0 0 1S, and all measurements were carried out at 300 K. The laser wavelength used in this study (514.5 nm) implies a high light absorption in the Al x Ga y In 1ÀxÀy As layers. The corresponding Raman probing depth for Ga y In 1Ày As is between 15 and 55 nm, depending on indium composition [6]. For the SAG samples, Raman cartography across the mask aperture, at a lateral resolution of 1 mm, was performed to study the spatial variation of the phonon peaks.…”