Materials Science in Semiconductor Processing 8 (2005) 383–388 Noise behavior of SiGe n-MODFETS A. Rennane a,b,Ã , L. Bary a , G. Cibiel a , O. Llopis a , T. Hackbarth c , J. Graffeuil a,b , R. Plana a,b a LAAS-CNRS, 7 Avenue du Colonel Roche-31077 Toulouse, France b Universite´Paul Sabatier, 118 Route de Narbonne-31078 Toulouse, France c Daimler Chrysler Research Center, Ulm, Germany Available online 10 November 2004 Abstract This paper presents an investigation of the low-frequency noise properties of SiGe-based on n-MODFETs through the characterization of both the gate current noise and the drain current noise, including their correlation. Measurements vs. bias and gate geometry have shown that this noise is generated through mobility fluctuations or carrier diffusion at the gate terminal when carrier number fluctuations are involved for drain current fluctuations. Residual phase noise measurements have shown that the up-conversion effect mainly occurs on the drain current noise. r 2004 Elsevier Ltd. All rights reserved. Keywords: n-MODFETS; Low-frequency noise; SiGe; Residual phase noise measurement; Mobility fluctuations; Carrier number fluctuations 1. Introduction SiGe technology introduces band-gap engineering and allows a flexible design of devices for RF applications. Si/SiGe-based modulation doped field effect transistors (MODFETs) or heterostructure field effect transistors (HFETs), respectively, have previously demonstrated excellent noise performances [1,2], and with quantum well confinement appear to be well suitable for high- frequency performances [3,4]. The aim of this work is to present the results of the low-frequency noise (LFN) of Si/SiGe n-type MODFETs. LFN characterizations of SiGe n-MODFETs are usually carried out by measuring the drain current noise S ID . In this paper, we mainly report the gate current noise S IG from SiGe n- MODFETs vs. bias and gate geometry in order to get a physical insight of the noise sources. Section 2 of this paper will briefly describe the test set that has been used to perform the full two port characterization. Section 3 will address a short description of the devices under discussion. Section 4 will present the results concerning the noise analysis that have been carried out while Section 5 will outline the conclusions of this paper. 2. LFN test set A transistor is a two port device and an exhaustive noise characterization necessitates the measurement of two noise generators including their correlation. Several methods are available. One consists of measuring the noise at the output terminal for various input termina- tion and to refer the noise to the input through an appropriate numerical method. This method consists of describing the noise behavior of the device through the ARTICLE IN PRESS 1369-8001/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mssp.2004.09.107 Ã Corresponding author. LAAS-CNRS, 7 Avenue du Colonel Roche-31077 Toulouse, France. Tel.: +00 33 5 61 33 62 09; fax: +00 33 5 61 33 69 69. E-mail address: arennane@laas.fr (A. Rennane).