On wafer‐scaled GaAs HEMTs: Direct and robust small signal modeling up to 50 GHz

Abstract

This article is aimed at extracting an accurate multibias small signal equivalent circuit for on‐wafer microwave HEMTs, which are based on AlGaAs/GaAs heterostructure. The main advantage of the on‐wafer characterization consists of having the possibility to determine the real microwave performance of the transistors, since the inclusion of additional parasitic effects, such as in the case of the packaging and wire bonding, are avoided. The presented small signal modeling technique is direct. As a matter of fact, the equivalent circuit elements are extracted from scattering parameter measurements by using only analytical formulas, without any optimization procedures. The validity of the obtained circuit models is successfully verified by comparing simulated and measured data of scaled GaAs HEMTs up to 50 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1958–1963, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24492

On the noise measurements and modeling for on wafer HEMTs up to 26.5 GHz

“…Extraction of all extrinsic circuit elements from S-parameters measured on the device under ''cold'' pinch-off condition (i.e., V DS ¼ 0 V and V GS < V PO ) and appropriate frequency range [11]. ii.…”

“…Determination and validation of an accurate microwave small signal and noise model for microwave solid state devices is mandatory for optimizing the design of reliable low-noise amplifiers operating in the microwave frequency range [1][2][3][4][5][6][7][8][9][10][11][12]. For that reason, we report here on measurements of scattering (S-) parameter and 50 X noise figure, respectively up to 50 GHz and 26.5 GHz, for on wafer AlGaAs/GaAs HEMTs with different gate width.…”

“…A circuit model is extracted to reproduce the measured behavior of the investigated devices. In particular, it should be pointed out that the extension of the model with the nonquasi-static effect associated to the gate-drain resistance and its associated temperature is necessary for obtaining a good agreement between model simulations and measurements at such high frequencies [7,8,11,12].…”

“…The condition to obtain the retrodirective property is conjugating the incoming wave phase in each array element [11]. Van Atta array reaches this property by the interconnection between radiators and the physical placement of elements, in this case an array of radiators is connected in pairs, each one is disposed around of a common center arranged symmetrically.…”

“…Besides, each interconnection must have the same electric length [12]. The heterodyne technique also known as Pon array [11] uses mixers to obtain the retrodirective property, as it is appreciated in Figure 1. If the incoming wave in the i-th element has a frequency x RF and phase h i , and the local oscillator (LO) frequency is 2x RF , then at the mixer output there are fundamentally two components: One is at frequency x RF with phase (h i , and the other is at 3x RF .…”