Low Frequency and linear high frequency noise performances of AlGaN/GaN grown on SiC substrate J.-G. Tartarin 1 , G. Soubercaze-Pun 1 , L. Bary 2 , C. Chambon 1 , S. Gribaldo 1 , O. Llopis 2 , L. Escotte 1 , R. Plana 1 , S. Delage 3 , C. Gaquière 4 , J. Graffeuil 1 1 LAAS-CNRS and Paul Sabatier University, 7 av. du Colonel Roche, 31.007 Toulouse cedex 4, France, 33 (0)561.336.456 2 LAAS-CNRS, 7 av. du Colonel Roche, 31.007 Toulouse cedex 4, France, 33 (0)561.336.209 3 TIGER, THALES, Orsay, domaine de Corbeville, France, 33 (0)169.330.802 4 TIGER, IEMN, 59.652 Villeneuve d’Ascq France, 33 (0)169.330.802 Abstract — Newly developed GaN technology offers great potential for military and space, as well as some high volume applications. The devices are grown on different substrates (sapphire, silicon and silicon carbide), involving differences on the performances, price, and technological complexity. The design of a fully integrated transceiver in such a technology necessitates great noise performances for the linear (Low Noise Amplifiers, LNA) and non-linear (Voltage Controlled Oscillator, VCO) applications. The low noise figure already published on this technology up to X- band, associated to the capability to handle high power levels avoid the integration of a limiter stage that deteriorates the overall noise figure in conventional architectures. The low frequency noise performances are useful both for the technology assessment (maturity’s indicator) and for the non-linear circuit design (conversion to phase noise around the carrier). This paper presents the noise performances of AlGaN/GaN HEMT grown on SiC substrate. Low frequency noise contributors in the Ohmic and saturated regime are discussed. Residual phase noise characterization at 10 GHz correlates the results about the noise sources involved, and linear high frequency noise figure measurements are also presented, targeting respectively VCO and LNA applications. I. INTRODUCTION High microwave power levels are typically required by microwave communication systems, satellite systems, remote sensing systems, and electronic warfare. If wide band-gap technologies were firstly dedicated to power applications (solid state power amplifiers), their development have also demonstrated good noise figures [1][2]. This technology can benefit from noise performances that thus should widen its application range both for the transmitter and receiver modules. These modules are supposed to be robust, with improved reliability against external RF aggression thanks to the higher band-gap energy and higher breakdown voltages than for narrow band-gap technologies. This paper proposes a general view on AlGaN/GaN HEMT noise performances and properties through non-linear and linear noise characterizations: this make up the basics for circuit design such as VCO and LNA, as well as PA for a fully integrated transceiver. Circuit designs have been reported featuring performances that can be correctly compared with well established SiGe and III-V MMIC [3][4]. Moreover, if low frequency noise (LFN) characterization is usually developed to improve the process quality, and thus the device’s dynamic and reliability characteristics, it is also a major indicator of the spectral purity of the RF carrier for the oscillator design. Devices have been investigated for different kind of substrates (Al 2 O 3 , Si, SiC), and the main contribution to the noise was found to occur in the two dimension electron gas (2DEG) under the active gate [5][6][7]. The performances of HEMT grown on sapphire and silicon substrates exhibit Hooge parameters of respectively 4.10 - 3 and 10 -4 : the difference has been attributed to a higher degree of dislocations in the channel when using silicon substrate. Only the flicker 1/f contribution was found for the spectra from the two later substrates. The present study focuses on devices on SiC substrates. The static and dynamic performances are described in the second paragraph. The two next paragraphs are related to non- linear noise measurements (LFN and residual phase noise). Then, some linear high frequency performances are presented to complete this noise characterization. II. DEVICES ON SIC: SOME PERFORMANCES The HEMT devices grown on silicon carbide substrate feature 24% aluminum content in the 2 DEG layer, and have been processed using the MOCVD technique [8]. Static and pulsed measurements have been largely performed respectively with HP4142 modular source and DIVA D225 system, on a large number of samples to appreciate the scattering of the electrical performances over the wafer. Substrate type SiC I DSS (saturation drain current, mA/mm) 1000 V T (threshold voltage, V) -5.5 Gm max (transconductance, mS/mm) 250 I G (gate leakage currents, µA) <0.1 R ON resistance (@V GS =0V, ohmic regime, ) 25 Ft and Fmax (GHz) 40-100 TABLE 1: HEMT (2x0.15x50 µm² gate area) static and dynamic parameters (mm unit refers to the normalization versus the gate width of the devices). 13 th GAAS  Symposium - Paris, 2005 277