IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 64, NO. 5, MAY 2016 1351 Characterization of Parasitic Resistances of AlN/GaN/AlGaN HEMTs Through TCAD-Based Device Simulations and On-Wafer Measurements Nandha Kumar Subramani, Amit Kumar Sahoo, Jean-Christophe Nallatamby, Raphael Sommet, Nathalie Rolland, Farid Medjdoub, and Raymond Quéré, Fellow, IEEE Abstract— This paper shows a detailed characterization and estimation of the temperature-dependent on-resistance R ON (T ) of AlN/GaN/AlGaN high electron-mobility transistors (HEMTs) through dc and low-frequency (LF) S-parameter measurements. The measurements are carried out at different chuck temper- atures (T chuck ) and the R ON (T ) is calculated for different values of gate–source bias (V GS ) of HEMT grown on a sil- icon carbide (SiC) substrate. Furthermore, we also present the two-dimensional (2-D) physics-based numerical simulation results for the R ON (T ) extraction of this device. Knowing R ON (T ) values of the device for different source–drain lengths ( L SD ), we propose a simplified method to extract the temperature-dependent series contact resistance R se (T ) and channel sheet resistance R sh (T ) of the GaN HEMT technology. Index Terms— Gallium-nitride (GaN), high electron-mobility transistor (HEMT), numerical simulation, on-resistance, sheet resistance. I. I NTRODUCTION T HE limitations of conventional semiconductors for RF and microwave power applications have paved the way for wide-bandgap group III–V materials such as GaN, SiC, etc. Among these, GaN material receives much attention due to its superior material properties [1], [2] such as high electron mobility, high saturation velocity, and high breakdown electric field. AlGaN/GaN high electron-mobility transistors (HEMTs) have proven to be an excellent candidate for high-power microwave and mm-wave applications [3]. Moreover, in recent years, the demand for high-frequency performance Manuscript received October 28, 2015; revised January 6, 2016, March 26, 2016, and March 29, 2016; accepted March 29, 2016. Date of publication April 20, 2016; date of current version May 10, 2016. This work was supported by the Agence Nationale de la Recherche (ANR), France, under Contract ANR-13-ASTR-0022 (CROCUS project). This paper is an expanded version from the IEEE MTT-S International Workshop on Integrated Nonlinear Microwave and Millimetre-wave Circuits, Taormina, Italy, October 1–2, 2015. N. K. Subramani, J.-C. Nallatamby, R. Sommet, and R. Quéré are with the CNRS, XLIM, UMR 7252, University of Limoges, F-19100 Brive, France (e-mail: nandhakumar2005@gmail.com; jean-christophe.nallatamby@ unilim.fr; Raphael.Sommet@xlim.fr; raymond.quere@xlim.fr). A. K. Sahoo was with the CNRS, XLIM, UMR 7252, University of Limoges, F-19100 Brive, France. He is now with Altis Semiconductor, 91105 Corbeil-Essonnes, France (e-mail: amit7phy@gmail.com). N. Rolland and F. Medjdoub are with IEMN/CNRS, 59650 Villeneuve d’Ascq, France (e-mail: nathalie.rolland@iemn.univ- lille1.fr; farid.medjdoub@iemn.univ-lille1.fr). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TMTT.2016.2549528 of AlGaN/GaN HEMT devices are steadily increasing [4]. In order to extend the frequency of operation of these devices, it is necessary to implement ultra-short gate lengths and using of thin AlGaN barrier [5]. However, reducing the thickness of the AlGaN barrier below a certain limit (about 10 nm) results in a strong degradation of the two-dimensional electron gas density (2DEG) and, thus, poor device performance [6]. Although increasing the Al content in the AlGaN barrier layer can improve the 2DEG density, it also increases the lattice mismatch between the AlGaN and GaN layers, thereby degrading the quality of the heterostructure [7]. Furthermore, implementing the gate recess technique on these devices is difficult and this generally induces high gate leakage and reliability problems [6]. In recent years, AlN/GaN HEMT technology has become popular owing to its high theoretical 2DEG density of 6 × 10 13 cm −2 [8]. This is due to the high spontaneous polarization value of AlN material [9] and its wide bandgap of 6.2 eV compared to GaN (3.42 eV). It has been demonstrated [10] that the replacement of the conventional AlGaN barrier layer by AlN/GaN layers offers much higher 2DEG density, allowing the achievement of high drain current (2 A/mm), even using ultra-thin AlN barrier layer thickness well below 10 nm. Furthermore, the AlN/GaN HEMT devices achieve high breakdown voltages and lower on-resistance [11]. This could be a suitable alternative to replace the existing conventional AlGaN/GaN HEMT tech- nology for high-frequency applications. Obtaining a very low on-resistance ( R ON ) immediately after switching from a high-voltage OFF state to a low-voltage ON state is a critical requirement in power electronics appli- cations [12]. The higher electron mobility in the 2-D quantum well presents a low R ON value that enhances the RF power- added efficiency performance [13]. In RF power GaN HEMT devices, dynamic switching issues occur due to current col- lapse, gate lag, and drain lag effects, which deteriorates the RF power performance [14]. In power switching applications, this issue is visible, where the R ON remains high for a period of time after an OFF–ON switching event [15]. In addition, the temperature has a significant impact on R ON . The reduction of the 2DEG mobility with the increase in temperature con- tributes to the increase in R ON [16]. Moreover, a power switch- ing transistor usually operates at a relatively high temperature. 0018-9480 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.