J Phys. Ivfrance12 (2002) pr3-117 © EDP Sciences, Les Uhs Do1 10 lost/jp420020048 DC and llf noise characterization of cryogenically cooled pseudomorphic HEMT'S G. Ferrante~~~, F. Pnncipato~~ A. Caddemi~, N. Donato~ and G. Tuccari~ Dipartimento di Fisica e Tecnologie Relative, Universitd di Palermo, Viale delle Scienze, go128 Palermo, Italy ~ lstituto Nazionale per la Fisica delta Materia, Unitb di Palermo, Facoltb di Engegneria, Viale delle Scienze, 90128 Palermo, Italy ~ Dipartimento di Fisica delta Matena e Tecnologie Fisiche Avanzate and INFM, Universitd di Messina, Contrada Sperone, 31 S. Agata, 98166 Messina, Italy ~ lstituto di Radioastronomia IRA-CNR, Contrada Renna, 96017 Noto, Italy Abstract: Pseudomorphic (AIGaAs/InGaAs/GaAs) HEMT'S have exhibited the best noise performance over the entire LF-to-microwave fieciuency range if compared to MESFET'S and conventional GaAs HEMT'S, due to either a reduced flicker noise, a lower G/R contrtbution and a smaller high-field diflbsion noise. We have recently investigated the microwave (up to 18 GHz) noise properties of packaged pseudomorphic HEMT'S from 290 K down to cryogenic temperature values The current experimental work is aimed at extending such analysis to the LF noise range and at low temperatures Cryogenic noise spectra (I Hz to 100 KHz) and DC characteristics have therefore been recorded and the relevant observations on the device behavior are herewith reported. 1.INTRODUCTION The performance of any microwave down-converter strongly depends on the noise properties of the active devices employed in the pre-amplifier, in the rn&er and in the local oscillator. Hence, the noise characteristics of a given device type have to be care&fly investigated over a broad frequency range because the microwave noise figwe directly affects the receiver sensitivity, whereas the up-conversion of the low-frequency (LF) noise limits the spectral pwity of non-linear circuits. From the viewpoint of the LF noise performance, Si bipolar transistors and SiGe heterojunction bipolar transistors are preferable devices because they are bufl~-type devices and are less affected by the swface conditions. However, high electron mobility transistors (HEMT) have better microwave performance and suitability for multdbnction applications when integrated on a single chip. In addition, it has been shown that a lower phase noise can be achieved in HEMT oscillators due to the better noise up-conversion factor than in HBT'S. Such up-conversion factor is mainly responsible for LF noise conversion into residual phase noise around the microwave carrier Ii. Prey studies have shown that pseudomorphic (AIGaAS/lnGaAs/GaAS) HEMT'S are characterized by the best noise performance over the entire LF-to-microwave frequency range if compared to Shottky-metal gate FET'S and conventional GaAs HEMT'S, due to either a reduced flicker noise, a lower G/R contribution and a smaller high-field dwsion noise [2]. Owing to the scientific interest in super low-noise front-ends for advanced telecommunication and space- qualified applications, we started to investigate the microwave (up to 18 GHz) noise properties of packaged pseudomorphic HEMT'S from 290 K down to cryogenic temperature values [3,4]. The current part of this experimental study is aimed at acquiring additional knowledge of the noise performance of the same device type in the low frequency (I Hz to 100 KHz) range, as a &nction of temperatwe between 50 and 300 K. 2. EXPEIIIMENTAL SET-UP AND METHODOLOGIES The devices analyzed are packaged pseudomorphic HEMT'S (MGF 4318 and MGF 4919G, by Mitsubishi)