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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,...
We present a new bonding process for gallium nitride (AlGaN/GaN) devices from Si onto diamond substrates. In our technology AlGaN/GaN-devices are transferred from silicon (Si) onto single (SCD) and polycrystalline diamond (PCD) substrates by van der Waals bonding. Load-pull measurements on Si and sCd at 3 GHz and 50 V drain bias show comparable power-added-efficiency (PAE) and output power (Pout)...
A current injection efficiency model is developed to identify and understand the limiting factors of the internal quantum efficiency in the GaN:Eu based red LEDs. Through this model the design and fabrication of high efficiency GaN:Eu devices in the red spectra regime is feasible.
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...
First-Principle analysis of the band structures for dilute-anion BN-based semiconductor was performed, and the findings indicated a direct bandgap properties of this alloy in deep ultraviolet regime as compared to the indirect band gap BN alloy.
This presents DC electrical characteristics and reliabilities of AlGaN/GaN metal-oxide-semiconductor heterojunction-field-effect transistors (MOS-HFETs) with HfO2 gate dielectric deposited by atomic layer deposition (ALD). Two types of oxidants were investigated, namely, water (H2O) and ozone (O3) for the ALD deposition. The comparison study reveals that GaN MOSHFETs with O3 oxidant results in overall...
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...
We present optimized THz detectors based on AlGaN/GaN field-effect transistors with integrated broadband bow-tie antennas (bow-tie TeraFETs). Designed with a comprehensive circuit model and fabricated with a recently developed AlGaN/GaN MMIC process, the devices reach a performance at room temperature which hitherto has only been achieved with Si CMOS TeraFETs. Capable of broadband detection from...
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...
Light emission characteristics of ultraviolet (UV) BGaN/AlN quantum well (QW) structures were investigated using the multiband effective-mass theory and non-Markovian model. The BGaN/AlN QW structures show a much larger light intensity than the conventional AlGaN/AlN QW structures. This is mainly due to the fact that the internal field is significantly reduced by increasing boron contents. The spontaneous...
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