Investigation of the use of MOSHEMT based amplifiers in direct receivers for radiometry applications

In recent years, advancement in the field of monolithic millimeter-wave integrated circuit (MMIC) technology has prompted advanced research once again in the field of passive imaging radiometers. Satellite passive microwave observations of surface brightness temperature are critical to describing and understanding Earth system [1]. Also, millimeter-wave imaging systems provide high spatial and temperature resolution while penetrating obscurants such as dust, fog, and clothing, thereby making them ideal for use in security scanners or collision avoidance systems [2]. However, achieving a typical threshold of noise equivalent temperature difference (NETD) as low as 0.5 K is still challenging for the current 0.1 THz radiometers on silicon substrate [3]. Hence, metamorphic high electron mobility transistor (mHEMT) based low noise amplifiers (LNAs) and detector are used in passive imaging radiometry receivers using technologies developed at Fraunhofer Institute for Applied Solid State Physics (IAF). As it is possible to achieve excellent performance with NETD = 0.45 for an integration time of 3.125 ms and 32 pixels [4]. However, mHEMT technology is also reaching its limit with the scaling of the gate length and is not able to fulfill the expected improvements in performance. Therefore, indium gallium arsenide (InGaAs) metal oxide semiconductor HEMT (MOSHEMT) technology is being developed with the aim to improve performance without restriction on the scaling of the transistors. MOSHEMT fulfills the desired qualities of high gain, high ft and low noise figure without limiting gate length [5]. However, the NETD and integration time of the receivers are critically affected by the flicker noise usually present below 10 MHz. Transistor models with correct electrical and noise performance can help predict and compensate noise on the output performance of the receiver. Computer-aided design of modern integrated microwave circuits requires an accurate model of the transistors in order to reliably simulate the behaviour of the circuits. This leads to fewer design cycles to reach target performance. This thesis is about the investigation and modeling of the flicker noise in new InGaAs MOSHEMT technology and comparing with the well-known mHEMT technology. An empirical noise model has been designed with validation from the on-wafer measurements. The employed model shows high accuracy for mHEMT and MOSHEMT technology with certain drain current bias