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The In<sub>x</sub>Ga<sub>1-x</sub>N films were characterized via spectroscopic ellipsometry using the lab's [[QAS Ellipsometer|J.A. Woollam Co. vertical-variable angle spectroscopic ellipsometer]] (V-VASE) with a photon range of 0.8 eV to 4.5 eV.
The In<sub>x</sub>Ga<sub>1-x</sub>N films were characterized via spectroscopic ellipsometry using the lab's [[QAS Ellipsometer|J.A. Woollam Co. vertical-variable angle spectroscopic ellipsometer]] (V-VASE) with a photon range of 0.8 eV to 4.5 eV.


In order to extract useful information about the thin films using ellipsometry, a Kramers-Kronig consistent parametric model was developed to fit the raw ellipsometric through a regression-based data analysis. In building the parametric model, each unique layer of material in the sample must be represented: Si wafer, SiO<sub>2</sub> substrate (grown on the Si wafer), In<sub>x</sub>Ga<sub>1-x</sub>N layer and a surface roughness layer (treated as a Bruggeman Effective Medium Approximation consisting of a 50/50 mixture of In<sub>x</sub>Ga<sub>1-x</sub>N film and void space. In order to represent the unique absorbing In<sub>x</sub>Ga<sub>1-x</sub>N layer, parametric dispersion relationships were used. A Cauchy layer with Urbach absorption was first used over the non-absorbing (transparent) regions of the ellipsometric data output. In order to produce a real physical shape for dispersion over the entire energy range (absorbing regions now included), the Cauchy layer was converted into a general oscillator layer using 2-3 Gaussian oscillators to enforce Kramers-Kronig consistency.
 
In order to extract useful information about the thin films using ellipsometry, a Kramers-Kronig consistent parametric model was developed to fit the raw ellipsometric through a regression-based data analysis. In building the parametric model, each unique layer of material in the sample must be represented: Si wafer, SiO<sub>2</sub> substrate (grown on the Si wafer), In<sub>x</sub>Ga<sub>1-x</sub>N layer and a surface roughness layer (treated as a Bruggeman Effective Medium Approximation consisting of a 50/50 mixture of In<sub>x</sub>Ga<sub>1-x</sub>N film and void space. In order to represent the unique absorbing In<sub>x</sub>Ga<sub>1-x</sub>N layer, parametric dispersion relationships were used. A Cauchy layer with Urbach absorption was first used over the non-absorbing (transparent) regions of the ellipsometric data output before being converted to a real physical relationship using Gaussian oscillators.  
 


Top-down and cross-sectional SEM images were taken using a [[Field emission scanning electron microscope lab protocol at Queen's University|field-emission scanning electron microscope (SEM)]] in the Queen's Physics Department.
Top-down and cross-sectional SEM images were taken using a [[Field emission scanning electron microscope lab protocol at Queen's University|field-emission scanning electron microscope (SEM)]] in the Queen's Physics Department.
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