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High electron mobility transistor (HEMT) biosensors hold great potential for realizing label-free, real-time, and direct detection. Owing to their unique properties of two-dimensional electron gas (2DEG), HEMT biosensors have the ability to amplify current changes pertinent to potential changes with the introduction of any biomolecules, making them highly surface charge sensitive. This review discusses the recent advances in the use of AlGaN/GaN and AlGaAs/GaAs HEMT as biosensors in the context of different gate architectures. We describe the fundamental mechanisms underlying their operational functions, giving insight into crucial experiments as well as the necessary analysis and validation of data. Surface functionalization and biorecognition integrated into the HEMT gate structures, including self-assembly strategies, are also presented in this review, with relevant and promising applications discussed for ultra-sensitive biosensors. Obstacles and opportunities for possible optimization are also surveyed. Conclusively, future prospects for further development and applications are discussed. This review is instructive for researchers who are new to this field as well as being informative for those who work in related fields.

Conventional pseudomorphic high electron mobility transistor (pHEMTs) with lattice-matched InGaAs/InAlAs/InP structures exhibit high mobility and saturation velocity and are hence attractive for the fabrication of three-terminal low-noise and high-frequency devices, which operate at room temperature. The major drawbacks of conventional pHEMT devices are the very low breakdown voltage (xGa(1−x)As (x = 0.53 or 0.7) channel material plus the contribution of other parts of the epitaxial structure. The capability to achieve higher frequency operation is also hindered in conventional InGaAs/InAlAs/InP pHEMTs, due to the standard 1 μm flat gate length technology used. A key challenge in solving these issues is the optimization of the InGaAs/InAlAs epilayer structure through band gap engineering. A related challenge is the fabrication of submicron gate length devices using I-line optical lithography, which is more cost-effective, compared to the use of e-Beam lithography. The main goal for this research involves a radical departure from the conventional InGaAs/InAlAs/InP pHEMT structures by designing new and advanced epilayer structures, which significantly improves the performance of conventional low-noise pHEMT devices and at the same time preserves the radio frequency (RF) characteristics. The optimization of the submicron T-gate length process is performed by introducing a new technique to further scale down the bottom gate opening. The outstanding achievements of the new design approach are 90% less gate current leakage and 70% improvement in breakdown voltage, compared with the conventional design. Furthermore, the submicron T-gate length process also shows an increase of about 58% and 33% in fT and fmax, respectively, compared to the conventional 1 μm gate length process. Consequently, the remarkable performance of this new design structure, together with a submicron gate length facilitatesthe implementation of excellent low-noise applications.

This paper presents the simulation and measured results of a Low Noise Amplifier (LNA) working at 28 GHz for the 5G wireless system. LNA is used to amplify the weak receiving signals in the RF receiver system. The 28 GHz (Ka-band) LNA is designed to work for 5G technology wireless system. Here a Fujitsu FHR02X transistor is used in the simulation process, where the one-stage LNA is adopting a common-source with source inductive degenerative topology.In the fabrication process, GaAs pHEMT MMIC HMC519LC4 LNA is mounted on the Rogers 4003C board (εr = 3.38 and δ = 0.0027)and tested using (PNA-X N5246A) Microwave Network Analyzer. The final LNA design in the simulation process achieves a power gain of 9.185 dB, input and output return losses of – 13.124 dB and – 15.455 dB respectively, and noise figure of 9.185 dB. Furthermore, the fabricated LNA achieves a power gain of 10.91 dB, input and output return losses of - 7.75 dB and - 22.13 dB respectively. Although the return loss (S11) value is higher than -10 dB, but the LNA still able to obtain gain more than 10 dB.Thesimulation and fabricated LNA have input return loss quite closed to the given value in the datasheet. Thus, the LNA transmission line has a good output matching design.