Power and noise performance of the pseudomorphic modulation doped field effect transistor at 60 GHz

Abstract

Quarter micron gate length In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.15</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.85</inf> As/Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.15</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.55</inf> As pseudomorphic modulation doped field effect transistors (MODFETs) were grown, fabricated, and characterized. These devices exhibit outstanding DC performance with excellent pinch-off characteristics, a relatively low output conductance for a quarter micron gate field effect transistor (FET), a high reverse breakdown voltage, and transconductances as high as 495 mS/mm at 300K. Furthermore, these devices show outstanding rf performance as well. At 18 GHz, a noise figure of 0.9 dB with an associated gain of 10.4 dB was observed, and at 62 GHz, the noise figure was 2.4 dB with an associated gain of 4.4 dB. Power measurements at 62.2 GHz indicate a maximum output power density of 0.43 W/mm (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</inf> = 6 V) with a power gain of 3 dB, and a maximum power added efficiency of 28%, an unprecedented value. When tuned a maximum available gain of 11.7 dB was obtained at 60 GHz implying a maximum frequency of oscillation near 250 GHz. From these results it is clear that the pseudomorphic MODFET represents a very attractive choice for operation near or above 60 GHz.