Electron transport properties in Al 0.25Ga 0.75N/AlN/ GaN heterostructures with different InGaN back barrier layers and GaN channel thicknesses grown by MOCVD

The electron transport properties in Al 0.25Ga 0.75N/AlN/GaN/In xGa 1-xN/GaN double heterostructures with various indium compositions and GaN channel thicknesses were investigated. Samples were grown on c-plane sapphire substrates by MOCVD and evaluated using variable temperature Hall effect measurements. In order to understand the observed transport properties, various scattering mechanisms, such as acoustic phonon, optical phonon, interface roughness, background impurity, and alloy disorder, were included in the theoretical model that was applied to the temperature-dependent mobility data. It was found that low temperature (T<160K) mobility is limited only by the interface roughness scattering mechanism, while at high temperatures (T>160K), optical phonon scattering is the dominant scattering mechanism for AlGaN/AlN/GaN/InGaN/GaN heterostructures. The higher mobility of the structures with InGaN back barriers was attributed to the large conduction band discontinuity obtained at the channel/buffer interface, which leads to better electron confinement. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Clinical and demographic features of hidradenitis suppurativa: a multicentre study of 1221 patients with an analysis of risk factors associated with disease severity.

Background Hidradenitis suppurativa (HS) is a chronic, relapsing and debilitating inflammatory disease associated with profound morbidity