Due to its excellent material performance, the AlGaN/GaN high-electron-mobility transistor (HEMT) provides a wide platform for biosensing. The high density and mobility of two-dimensional electron gas (2DEG) at the AlGaN/GaN interface induced by the polarization effect and the short distance between the 2DEG channel and the surface can improve the sensitivity of the biosensors. The high thermal and chemical stability can also benefit HEMT-based biosensors’ operation under, for example, high temperatures and chemically harsh environments. This makes creating biosensors with excellent sensitivity, selectivity, reliability, and repeatability achievable using commercialized semiconductor materials. To synthesize the recent developments and advantages in this research field, we review the various AlGaN/GaN HEMT-based biosensors’ structures, operations mechanisms, and applications. This review will help new researchers to learn the basic information about the topic and aid in the development of next-generation of AlGaN/GaN HEMT-based biosensors.

This work systematically investigates the electrostatic discharge (ESD) robustness of Schottky-gate p-GaN high electron mobility transistors (HEMTs) under different gate and drain bias conditions. Gate-terminal ESD robustness is severely compromised under high ${V}_{\text {DS}}$ ( $\ge 40$ V), where synergistic high voltage/current induces thermal runaway, causing irreversible damage. At ${V}_{\text {DS}} =5$ –30 V, trap-dominated ${V}_{\text {TH}}$ shifts (up to 0.68 V) correlate with $1200\times {N}_{\text {it0}}$ increases, partially recoverable over time. With the drain in the floating state, the trap-dominated ${V}_{\text {TH}}$ shift (about 0.47 V) correlate with $140\times {N}_{\text {it}}$ increases, nearly fully recoverable over time. Under the drain-terminal ESD events, the device with the gate in floating state exhibits superior ESD robustness, accompanied by only a 0.12-V negative ${V} _{\text {TH}}$ shift and high ${V}_{\text {HBM}}$ of over 8.61 kV. The devices with gate biased at off/semi-on/on states achieve ${V}_{\text {HBM}}$ from 0.27 to 30 kV, with (semi-on) on-state configurations meeting 2-kV industrial standards. This work bridges the gap in understanding multistress ESD interactions, providing critical insights for optimizing p-GaN HEMT reliability.

In this Letter, we investigate the threshold voltage (VTH) instability of Schottky p-GaN gate high electron mobility transistors (SP-HEMTs) under high-frequency operation by a resistive-load hard switching method. The abnormal VTH instability is observed, which is different between fully and partially depleted SP-HEMTs (FD- and PD-HEMTs). Notably, for FD-HEMT, VTH shifts positively with effective stress time. However, the VTH instability in PD-HEMT is more complex. At low VGS (e.g., 3 V) and high VGS (e.g., 6 V), VTH shifts positively with stress time consistently. Nevertheless, at intermediate VGS levels (e.g., 4 and 5 V), VTH initially shifts positively and then negatively, displaying a non-monotonous variation. Furthermore, the frequency dependence of VTH is contingent upon VGS. At low VGS, VTH exhibits a negative shift with the increase in frequency. This trend inverses when VGS exceeds 4 V. And it should be noted that the extracted VTH under high-frequency operation is lower than their quasi-static values for both transistor types. This work depicts the physical process and mechanism of the abnormal VTH instability; different from the quasi-static case, hole accumulation effects will be enhanced due to the high dV/dt, which results in a lower VTH. The distinct VTH behaviors of FD- and PD-HEMTs are closely related to the trapping effects, as well as hole accumulation and insufficiency, within the two different p-GaN gate layers.

In this article, the failure behavior and mechanism of p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs) in the third quadrant under repetitive surge current stress are investigated. Repetitive stress tests with different surge current peak values ( $\textit{I}_{\text{peak}}$ ) are carried out. At high $\textit{I}_{\text{peak}}$ , as the stress cycle increases, the evolution of the peak value of surge voltage induced by surge current shows an obvious turning phenomenon and a significant increasing trend. When the surge voltage reaches a certain value, the gate-to-source breakdown occurs, and then, the device is burned out. We propose that the degradation of the third-quadrant conduction characteristics results in the change of surge voltage, and excessive electric field intensity induced by high gate-to-drain voltage ( $\textit{V}_{\text{GD}}$ ) causes the gate Schottky junction breakdown. It is confirmed by further experiments, electrical performance characterization, and simulation. Inconsistent degradation of the two-dimensional electron gas (2DEG) channel in various regions causes the aforementioned turning phenomenon. As the stress cycle increases, the channel degradation in the gate-to-source/drain access region occupies a dominant position. In this situation, the $\textit{V}_{\text{GD}}$ increases continuously, which will enhance the tunneling effect at the Schottky junction, until breakdown occurs. Besides, the device shows better surge current reliability at higher gate-to-source voltage. These results provide important insights into the improvement of GaN HEMTs reliability.

This work investigates the threshold voltage ( V _th ) instability in Schottky-type p-GaN gate HEMTs subjected to positive/negative gate switching stress. Under the gate switching stress, a characteristic “M”-shaped V _th curve with elevated V _{GS, ON} is revealed. This pattern is ascribed to the competitive transport of electrons and holes. Considering the condition of reduced V _{GS, OFF} , an increasing V _th has also been observed, which is attributed to the curtailed electron emission while the promoted hole release. Further, with the increasing of the duty cycle, a positive V _th shift at the lower V _{GS, ON} and a negative shift at higher V _{GS, ON} are needs to be taken seriously, and it also confirm the competitive mechanism in the abnormal “M”-shaped V _th instability. The research highlights that the impact of positive/negative gate switching stress on V _th instability are significant and cannot be neglected.

This work first analyzes the failure behaviors of P-GaN HEMTs with different gate structures (Schottky gate vs. Ohmic gate) under both forward and reverse ESD stresses. It reveals that the Schottky gate structure lacks effective electrostatic charge discharge paths, which leads to the accumulation of transient charges generated by ESD stress in the gate terminal, resulting in significant transient overvoltage and ultimately causing breakdown failure. Subsequently, the paper systematically reviews three existing unidirectional ESD protection technologies based on the P-GaN HEMT platform. While these technologies can discharge transient electrostatic charges generated by both forward and reverse ESD stresses, they operate in diode mode during reverse ESD events, exhibiting excessively low reverse triggering voltage. Furthermore, unidirectional ESD protection structures based on resistive voltage division and diode voltage division introduce substantial forward and reverse leakage currents. Finally, the article evaluates four bidirectional GaN ESD protection technologies. These bidirectional structures can likewise discharge transient charges from both forward and reverse ESD stresses. Compared to unidirectional approaches, the key advantage of bidirectional ESD protection lies in its ability to provide an appropriate reverse triggering voltage during reverse ESD events, thereby effectively clamping the reverse potential to the desired level. However, likewise, bidirectional ESD protection schemes based on resistive or diode voltage division also inevitably introduce relatively large forward and reverse leakage currents.