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In our previous studies, a AlGaN/GaN HEMTs (High Electron Mobilty Transistors) demonstrated a sharp drain current phenomenon in a cryogenic environment, which is not confirmed at room temperature. This phenomenon was not derived from the self-heating effect of GaN-HEMT but was considered as a current collapse phenomenon caused by crystal defects at the interface between i-GaN and AlGaN. In this study,...
This paper investigates substrate biasing effects in a monolithically-integrated half-bridge stage rated for 600 V/20 A and fabricated in a lateral AlGaN/GaN-on-Si technology. On-resistance degradation effects caused by the common substrate potential are analyzed and explained for the monolithic half-bridge stage operating in a 400 V-synchronous buck converter. The detailed analysis of an ungated...
In this study, the threshold voltage and breakdown voltage of a double-channel AlGaN/GaN HEMT is improved. Firstly, depletion mode (D-mode) is changed to enhancement mode (E-mode) by optimizing the depth of the recessed gate, the Al ratio in the AlGaN layer, and the doping concentration of the p-doped region. Secondly, the E-mode device with highest breakdown voltage is selected, and then implemented...
In this paper, we have explored the impact of different gate architectures in controlling short channel effects in scaled AlGaN/GaN HEMT devices using calibrated 2-D TCAD simulations. Devices with different gate topologies, namely I-Gate and T-Gate are investigated for their efficacy in minimizing the short channel effects. Various parameters like transconductance, channel conductance and drain induced...
This paper presents a simulation study to achieve wide-linear-range transconductance of T-gate GaN HEMTs by introducing a δ-doped layer and a p-GaN back barrier. With optimized δ-doping density and location, the transconductance (gm) and current gain cutoff frequencies (fT) are ultra-flat and remain close to their peak values over a wide range of gate-source voltages (Vgs). In addition, a smaller...
It is well known that a two-dimensional electron gas (2DEG) exists at the MgZnO/ZnO interface. Both the formation mechanism and the origin of this 2DEG is of immense interest. The origin has been attributed to the polarization charge present coupled with the donor-like surface states on the MgZnO surface. In this paper, a physics-based model is described to explain the 2DEG as well as the bare surface...
Extensive studies have concluded that breakdown mechanisms in Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT) can be improved by substrate reduction and the addition of field plate (FP) on their structures. A theoretical analysis of the FP effects on the HEMT is carried out by modeling the electric fields inside the structure. The electric field model is deduced by solving the potential...
The interplay of self-heating and polarization affecting the current is studied in Al0.32Ga0.68N/AlN/GaN/Al0.1Ga0.9N Transmission Line Model (TLM) heterostructures with a scaled source-drain distance. The study is based on meticulously calibrated TCAD simulations against I-V experimental characteristics using an electro-thermal model. The electro-thermal simulations show hot-spots at the edge of the...
Significant advances in AlGaN/GaN heterostructure based technologies in the last decade, with AlGaN/GaN high electron mobility transistors (HEMTs) has led to high power performance at Gigahertz frequencies for communication, space, radar, and defense applications. The conjunction of the remarkable properties of the AlGaN/GaN heterojunction and the high thermal conductivity of the silicon carbide substrate...
This paper reports on the layout optimization of Pt-AlGaN/GaN HEMT-sensors for enhancing hydrogen sensor performance. Sensors with gate width and length ratios Wg/Lg from 0.25 to 10 were designed, fabricated and tested for the detection of hydrogen gas at 200 °C. Sensitivity, sensing current variation and transient response are directly related to the sensor gate electrode Wg/Lg ratio. The obtained...
A high breakdown voltage AlGaN/GaN HEMTs is fabricated by using source-connected field plate (SCFP) in Dynax. The output capacitance (Cds) of this device shows a strong dependence on Vds. A modified Angelov large signal model considering Cds nonlinearity is presented to achieve a more accurate simulation on efficiency and linearity. The small signal simulation results indicate that the proposed nonlinear...
The bow-tie (BT) diodes with broken symmetry for room temperature terahertz detection were developed of AlGaN/GaN high electron mobility transistor (HEMT) structures with two dimensional electron gas (2DEG). The performance of new THz detectors was obtained at 0.3 THz frequency and compared with the most sensitive InGaAs-based BT diodes of the same design. Our experiments at sub-THz frequency revealed...
In this study, the maximum spatial resolution of infrared thermal imager is 3 μm, and the gate length of AlGaN/GaN HEMTs is between 0.2 μm and 1 μm. Therefore, the infrared thermal imaging instrument measurement results are only an average temperature that is lower than the actual temperature. By combining infrared thermal imaging with Sentaurus TCAD simulation, the junction temperature of AlGaN/GaN...
In this study, we investigate the Ron degradation in D-mode AlGaN/GaN MIS-HEMTs on a Si substrate via an accelerated step stress at different temperatures. We have observed a three-phase Ron degradation behavior, which is highly correlated with a drain bias and back gate bias. First, the Ron degradation increases till a peak value when the drain bias increases. Second, when the drain bias increases...
Strained heteroepitaxial HEMTs without the mechanical support of a substrate have been demonstrated only for small-sized AlGaN/GaN membranes, i.e., the substrate was removed from within the immediate vicinity of the transistor area [1]. Such transistors have exhibited improved breakdown voltage and frequency response. However, wafer-scale substrate removal has been considered detrimental to the heterostructure...
This paper demonstrates successful fabrication of AlGaN/GaN high-electron-mobility transistors (HEMTs) with an AlGaN barrier layer directly regrown on a reactive-ion-etched GaN layer. The HEMT device fabricated on a high-mobility (>1000 cm2/Vs) GaN channel exhibited fairly excellent pinched-off characteristics with a maximum drain current of 90 mA/mm, whereas the device fabricated on a low-mobility...
This paper describes suppression of current collapse by field-plate (FP) in AlGaN/GaN MOS-HEMTs. Current collapse reduction was confirmed for a multi-gate fingered MOS-HEMT with a total gate width of 10 mm. Moreover, we have fabricated a 5-A class MOS-HEMT with both gate-FP and source-FP (dual-FP), showing more complete suppression in current collapse as compared to that with only gate-FP.
We investigated zinc oxide (ZnO) nanostructure gated gallium nitride (GaN) heterostructure field effect transistor (HFET) devices and explored their potential application in chemical sensing and monitoring of human respiration. The ZnO nanostructures were grown on aluminum gallium nitride (AlGaN)/GaN heterostructures by a hydrothermal solution process. The atomic force microscopy (AFM) and scanning...
In this work, we report on high positive threshold voltage and respectable drain current density obtained from our AlGaN/GaN MIS-HEMTs with recessed-gate structure. After subjecting the device to reverse bias annealing, on top of improved subthreshold swing and leakage characteristics, its threshold voltage shifted from −0.2 V to +3.5 V. We have also confirmed that these desirable device characteristics...
Current dispersion is an issue in AlGaN/GaN HEMTs. Different methods have been reported to investigate this phenomenon. This study reports an investigation of intrinsic components from small-signal model of AlGaN/GaN HEMTs right after off-state bias in linear and saturation regions in addition to drain-lag measurement. Different variations on the intrinsic components after off-state bias in linear...
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