By combining a low damage chlorine based gate-recess etching and a sophisticated technology for AlGaN/GaN depletion-mode high electron mobility transistors (HEMTs) we fabricated high performance recessed enhancement-mode HEMTs. A comparative investigation of depletion-and enhancement-mode devices prepared by this technique shows excellent DC and RF properties. A transconductance of 540 mS/mm and cut-off frequencies f T of 39 GHz and f max of 74 GHz were obtained for 0.25 mm gate enhancement-mode HEMTs. Largesignal power measurements at 2 GHz reveal an output power density of 4.6 W/mm at 68% PAE conclusively demonstrating the capability of our enhancement-mode devices. #

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An empirical model for the effective electron mobility in silicon nanowires (SiNWs) is presented. The model is based on published mobility data from numerical simulations of electron transport in SiNWs with different cross sections. Both phonon scattering and surface roughness scattering as well as the impact of the effective vertical field are considered. A comparison with a variety of experimental mobility data from the literature shows that the model can be treated as a reference for benchmarking different NW technologies. The effective field dependence is modeled by a simple expression making our mobility model very efficient for the use in numerical device simulators or in analytical MOSFET models. Index Terms-Effective field, empirical model, mobility, MOSFET, phonon scattering, silicon nanowires (SiNWs), surface roughness (SR).

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