High-Accuracy Measurement of Mid-IR Refractive Indices of GaAs/AlGaAs in Thin-Film Multilayers

Perner, Lukas W.; Winkler, Georg; Truong, Gar-Wing; Follman, David; Fellinger, Jakob; Prinz, Maximilian; Puchegger, S.; Cole, Garrett D.; Heckl, Oliver H.

doi:10.1364/oic.2022.wa.5

Cited by 1 publication

(4 citation statements)

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“…The feasibility of the method is verified by an experimental study on a GaAs/Al x Ga 1-x As multilayer [20], which yields results in good agreement with previously-published results and propagated uncertainties on the 10 −4 level in the 2 to 7 µm spectral range. Here, an FTIR spectrometer is used to obtain the photometrically accurate transmittance spectrum and the accurate layer thicknesses are obtained via calibrated SEM metrology.…”

Section: Via X-ray Diffraction (Xrd)supporting

confidence: 80%

“…We choose an adequate dispersion model, based on the wavelength region and the material type. In general, we found that models with fewer parameters, such as the model developed by Afromowitz [28] used in our experimental study, are more robust against overfitting to remaining systematic measurement deviations (for details see [20]). However, the model needs to be able to capture expected dispersion variations adequately.…”

mentioning

confidence: 79%

“…As will be discussed in detail below, the proposed method involves three main steps: (i) measuring a photometrically-accurate (i.e., unaffected by systematic effects such as detector nonlinearity) transmittance (or reflectance) spectrum of a multilayer sample (ii) obtaining individual physical layer thicknesses from a cross-sectional measurement (iii) perform a bestfit routine using an appropriate model, as outlined by the schematic in Fig. 1 (a detailed report of each step is found in [20]). This routine yields a propagated standard uncertainty on the 10 −4 level for both materials.…”

mentioning

confidence: 99%

“…To demonstrate the feasibility and performance of this simultaneous refractive index measurement approach, we probed a MBE-grown crystalline GaAs/Al x Ga 1-x As multilayer structure [20]. Specimens previously produced by the same manufacturer under identical conditions were recently shown to have ultra-low absorption and scatter losses [8,12], making this material system an ideal sample.…”

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confidence: 99%

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Precise Measurement of Refractive Indices in Thin Film Heterostructures

Perner¹,

Truong²,

Follman³

et al. 2023

Preprint

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We present a robust, precise, and accurate method to simultaneously measure the refractive indices of two transparent materials within an interference coating. This is achieved by measuring both a photometrically accurate transmittance spectrum and the as-grown individual layer thicknesses of a thin-film multilayer structure. These measurements are used for a TMM-based curve-fitting routine which extracts the refractive indices and their measurement uncertainties via a Monte-Carlo-type error propagation. We demonstrate the performance of this approach by experimentally measuring the refractive indices of both, GaAs and Al 0.929 Ga 0.071 As, as present in an epitaxial distributed Bragg reflector. A variety of devices can be used to obtain the transmittance spectrum (e.g., FTIR, grating-based spectrophotometer) and layer thicknesses (e.g., SEM, TEM, AFM), the discussed approach is readily adaptable to virtually any wavelength region and many transparent material combinations of interest. The subsequent model-fitting approach yields refractive index values with 10 −4 -level uncertainty for both materials.

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Section: Via X-ray Diffraction (Xrd)supporting

confidence: 80%

mentioning

confidence: 79%

mentioning

confidence: 99%

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confidence: 99%

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