Isha Maini

Gallium nitride (GaN) transistors are a highly promising technology, with applications in high-frequency, high-temperature, and high-efficiency power systems. However, they are susceptible to various electromagnetic hazards. As a result, in-situ state-of-health (SOH) active monitoring of the device during operation is necessary, with various efforts focusing on non-invasive approaches. This study presents the design and testing of a complete, in-situ, non-invasive monitoring system powered by energy harvested from the GaN transistor’s power line (PL). Experimental results show that an external low-power load of approx. 3.6 W, such as a standard server fan, is sufficient to generate approximately 16 μW and 64 μW (i.e., for two different GaN transistors) of radiated power at the transistor’s drain connection with the PL. This emitted energy, harvested using a 100 mH inductor, is capable of powering a remote SOH monitoring system consisting of a Microchip PIC24F 16-bit microcontroller, three MCP9700 temperature sensors, and an MRF89XA 868 MHz transceiver. The resulting system is able to collect sensor data and, after a brief energy accumulation period (the system’s warm-start charging cycle), wirelessly transmit it to a base station. To further illustrate the practicality of the proposed SOH monitoring solution, the two GaN transistors were intentionally driven into a thermal runaway regime while operating in low-power mode on a 12 W load. Under these conditions, the harvested energy/emmited radiation increased to approximately 620 μW and 3,216 μW, representing about 38 and 50 times the values observed in the previous low-power demonstration, respectively.

The GaN Hall sensors are the latest advancements in non-intrusive active monitoring, designed to be integrated on GaN power transistors to enable in-situ condition monitoring, hence boosting device reliability and life. This paper describes step-by-step the basic procedures required for the fabrication of a three-terminal Hall-effect sensor on GaN, challenges and a robust testing method that can deliver consistent results when testing under diverse laboratory external hazards. This work is presenting the first three terminal current sensing GaN Hall sensor reported in literature, which have been tested at room temperature under various magnetic field intensities and polarities in order to determine its sensitivity. Since even when properly using the most suitable scientific equipment, errors may occur from insufficient information regarding the relative angle between the magnetic field and the active area of the sensor or, data records affected by imperceptible equipment vibrations, this work provides a practical solution on how to detect and mitigate these shortcomings: magnetic quasi-static sources alternatives are discussed and transient recordings of different intensities and polarities of the magnetic field are separated and interpreted similar with the spectrometry diagrams. This comprehensive presented study delivers a consistent testing framework for the new emerging generation of magnetic sensors.

In this work, a new Field Effect Transistor device concept based on hydrogen‐terminated diamond (H‐diamond) is demonstrated that operates in an Accumulation Channel rather than a Transfer Doping regime. The FET devices demonstrate both extreme enhancement‐mode operation and high on‐current with improved channel charge mobility compared to Transfer‐Doped equivalents. Electron‐beam evaporated Al₂O₃ is used on H‐diamond to suppress the Transfer Doping mechanism and produce an extremely high ungated channel resistance. A high‐quality H‐diamond surface with an unpinned Fermi level is crucially achieved, allowing for the formation of a high‐density hole accumulation layer by gating the entire device channel which is encapsulated in dual‐stacks of Al₂O₃. Completed devices with gate/channel length of 1 µm demonstrate record threshold voltage < −6 V with on‐current > 80 mA mm⁻¹. Carrier density and mobility figures extracted by CV analysis indicate a high 2D charge density of ≈ 2 × 10¹² cm⁻² and increased hole mobility of 110 cm² V⁻¹ s⁻¹ in comparison with more traditional Transfer‐Doped H‐diamond FETs. These results demonstrate the most negative threshold voltage yet reported for H‐diamond FETs and highlight a powerful new strategy to greatly improve carrier mobility and enable enhanced high power and high frequency diamond transistor performance.