In this work, we present multi-channel tri-gate AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs) for high-voltage applications. A heterostructure with multiple AlGaN/GaN layers was used to form five parallel two-dimensional-electron-gas (2DEG) channels to reduce the ON-resistance (R ON ), simultaneously modulated by the 3-dimensional trigate electrodes. The tri-gate is a unique technology to control the multi-channels, providing enhanced electrostatics and device performance, and, in turn, the multi-channels are exceptionally suited to address the degradation in drain current (I D,max ) caused by the tri-gate. With a tri-gate width (w) of 100 nm, normally-on multi-channel tri-gate transistors presented 3Â-higher maximum drain current (I D,max ), 47%-smaller R ON , as well as 79%-higher maximum transconductance (g m,max ), as compared to counterpart single-channel devices. Using the channel depletion through the tri-gate sidewalls, normally-off operation was also achieved by reducing w below the sidewall depletion width (w dep ), resulting in a positive threshold voltage (V TH ) of 0.82 V at 1 lA/mm. The devices presented a high breakdown voltage (V BR ) of 715 V, which reveals a promising future platform for high-voltage low-R ON GaN transistors. Published by AIP Publishing.
Here we report novel multi-channel AlGaN/GaN MOSHEMTs with high breakdown voltage (VBR) and low ONresistance (R ON). The multi-channel structure was judiciously designed to yield a small sheet resistance (R s) of 80 Ω/sq using only four 2DEG channels, resulting in an effective resistivity (ρ eff) of only 1.1 mΩ•mm. The major limitation of highconductivity multi-channel devices is their limited V BR. This work shows that while conventional field plates (FPs) are not suited to increase VBR in high-conductivity multi-channels, slanted tri-gates offer better electric field management inside the device. With a gate-to-drain separation (L GD) of 15 µm, the device presented a low RON of 2.8 Ω•mm (considering the full width of the device (wdevice)) and a high VBR of 1230 V, rendering a small specific R ON (R ON,SP) of 0.47 mΩ•cm 2 and an excellent figure-of-merit of 3.2 GW/cm 2. This work also shows the feasibility of E-mode multi-channel MOSHEMTs with a threshold voltage (V TH) of +0.9 V at 1 µA/mm by tuning the tri-gate geometry. These results significantly outperform conventional single-channel devices and demonstrate the enormous potential of multi-channel power devices.
Gallium nitride (GaN) power devices are employed in an increasing number of applications thanks to their excellent performance. Nevertheless, their potential for cryogenic applications, such as space, aviation, and superconducting systems, has not yet been fully explored. In particular, little is known on the device performance below liquid nitrogen temperature (77 K) and the behavior of popular GaN architectures such as Gate Injection Transistor (GIT) and Cascode below room temperature has not yet been reported. Most importantly, it is still unclear how the different device loss contributions, i.e. conduction, soft-and hard-switching losses, change at cryogenic temperatures. In this work, we investigate and compare the performance of four GaN commercial power devices in a wide temperature range between 400 K and 4.2 K. All of the tested devices can successfully operate at cryogenic temperature with an overall performance improvement. However, different GaN HEMT technologies lead to significant variations in device gate control and loss mechanisms, which are discussed based on the device structure. The presented results prove the promising potential of the GaN technology for lowtemperature applications and provide precious insights to properly design power systems operating under cryogenic temperatures and maximize their efficiency.
In this letter, we present normally-off GaN-on-Si MOSFETs based on the combination of tri-gate with a short barrier recess to yield a large positive threshold voltage (VTH), while maintaining a low specific on resistance (RON,SP) and high current density (I D). The tri-gate structure offered excellent channel control, enhancing the VTH from +0.3 V for the recessed to +1.4 V for the recessed tri-gate, along with a much reduced hysteresis in VTH, and a significantly increased transconductance (gm). Additional conduction channels at the sidewalls of the tri-gate trenches compensated the degradation in ON resistance (RON) from the gate recess, resulting in a small RON of 7.32 ± 0.26 Ω•mm for LGD of 15 μm, and an increase in the maximum output current (I D max). In addition, the tri-gate inherently integrates a gateconnected field-plate (FP), which improved the breakdown voltage (VBR) and reduced the degradation in dynamic RON. With proper passivation techniques, these devices could be very promising as high performance power switches for future power applications.
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