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A comprehensive model for the electron mobility in AlGaN lattices-matched to GaN is developed. A large number of experimental and theoretical mobility data and the results of Monte Carlo transport simulations in previous literature have been evaluated and referred as the basis for the model development. The proposed model describes the variation of the field-dependent mobility with carrier concentration,...
A Magnesium Doped Layer (MDL) under the 2-DEG channel and a Drain Metal Extension (DME) are proposed to provide a new degree of freedom in the optimization between breakdown voltage (BV) and specific-on-resistance (Ron-sp) in AlGaN/GaN HEMTs. The surface electric field of the proposed structure is distributed more evenly when compare to the MDL-only structure with the same dimensions. A breakdown...
The terahertz frequency GaN Gunn diodes with GaN and AlGaN electron launchers are investigated by using an improved NDM model of GaN. The simulations demonstrate that there exists a shift of the oscillation mode from dipole domain mode toward accumulation mode with increased temperature, and the AlGaN launcher GaN Gunn diode can generate better power performance at stable oscillation mode than the...
Well-aligned ZnO nanorods were grown on the p-GaN substrate by a hydrothermal method and n-ZnO nanorods/p-GaN heterojunction LED structures were formed. The electroluminescence (EL) properties of this structure were studied under both forward and reverse bias. The nanorod LED device only has light output under reverse bias. The I-V characteristic results show that the nanosized junction can increase...
The activation characteristics of Si ion-implanted gallium nitride (GaN) have been investigated. High-resolution X-ray diffraction (HRXRD) analyses indicate that ion-implanted damage can be effectively recovered by rapid thermal annealing (RTA) up to 1100°C. With the implantation dose 1016cm-2, the sample presents strong n-type conductivity, reaching a maximum sheet carrier concentration 2×1015cm-2...
It has been proposed in the literature to use metal field plates (FPs) in order to increase the breakdown voltage (BV) of AlGaN/GaN HEMTs. In this article we analyze the possibility of using multiple FPs to increase the gate-to-drain BV. We show that FPs with variable oxide thickness (with thinner oxide towards the gate electrode and thicker oxide thickness towards the drain electrode) increase the...
A novel hybrid-anode AlGaN/GaN field-effect rectifier (HA-FER) with low operation voltage has been proposed. The rectifier features a Schottky gate controlled channel between the cathode and anode, by integrating the recessed-Schottky gate and anode Ohmic contact together (hybrid-anode). The turn-on voltage of HA-FER is determined by the threshold voltage of the channel instead of the Schottky barrier,...
Dual gate AlGaN/GaN MOS HFET with Al2O3 as gate oxide layer was fabricated. In comparison with normal dual gate Schottky HFET, dual gate MOS HFET exhibits much lower gate leakage current, larger transconductance and output current. Besides, the dual gate MOS HFET shows excellent breakdown characteristic.
GaN is very promising for power switching transistors taking advantages of the high breakdown strength with high saturation electron velocity. The lateral and compact device configuration enables high speed switching with reduced on-state resistance and parasitic capacitance. In this paper, state-of-the-art device technologies of GaN transistor and its monolithic integration for switching applications...
The high breakdown voltage AlGaN/GaN HEMTs with source-terminated field plate was firstly fabricated for high frequency and high power application, employing by CF4 plasma treatment for enhancement-mode (E-mode). The results showed that by adding the distance of gate to drain, LGD from 5 um to 15um, the breakdown voltage of the device was rapidly increased 350V, whose value is from 50V to 400V while...
This paper presents a reliability evaluation of Schottky contact of AlGaN/GaN HEMT. The Schottky barrier height(SBH) and ideality factor are investigated through the current-voltage (I-V) characteristics. Two kinds of ac voltages with different frequencies (10 kHz and 1 MHz) are applied on the two similar Schottky contacts of AlGaN/GaN HEMT, and the I-V curves are measured. From the measured results,...
The influence of neutron irradiation on the deep levels in GaN epilayer is studied. Thermal stimulated current (TSC) and low temperature photoluminescence (PL) techniques are used to determine the position of deep levels. Four traps are found in irradiated GaN and five traps in unirradiated sample by resolving TSC spectrum. The activation energy (Et), capture cross section (St), and concentration...
High breakdown voltage GaN HEMTs was developed for power electronics application. The device with source connected field plate (FP) was fabricated, which demonstrated perfect hard breakdown characteristics. A high breakdown voltage of 740V was obtained in air ambient while gate-drain spacing Lgd and FP length LFP equaled to 20μm and 2μm respectively. Specific on-resistance of the device was 14mΩ.cm...
One way to increase the breakdown voltage in heterojunction field-effect-transistors (HFETs) on silicon substrate is to introduce a transition (buffer) layer made of a sandwich of thin AlN/AlGaN layers between the silicon substrate and the GaN well. The effect of this transition layer is to average out and, in this way, to reduce the local mechanical stress that appears between the silicon substrate...
InGaN/GaN multi-quantum-well (MQW) nanowires and accordingly light-emitting-diodes (LEDs) were fabricated on the n-GaN/sapphire substrate with a nano-patterned SiO2 film as growth mask. The structural characteristics, optical and electrical properties were investigated. the observed results show that a InGaN/GaN MQW nanowire has smooth surface morphologies and triangular cross sectional structure...
Compared with Ti/Al/Ni/Au Ohmic contacts, Ti/Al/Ti/Al/Ti/Al/Ti/Al/Ti/Al/Ni/Au with multiple Ti/Al stacks improved the thermal stability. Multiple-stacked Ohmic contacts showed lower degradation during long-time thermal aging at 600°C. The samples after degradation were tested with Transmission Electron Microscopy (TEM) to research the structural reasons. TEM results show that multiple stacks can avoid...
GaN “Smart Discrete” power devices were realized using the AlGaN/GaN-on-Si platform, where two built-in intelligent self-protection functions were demonstrated. First, an AlGaN/GaN normally-off high electron mobility transistor (HEMT) with reverse drain blocking capability was realized, featuring a Schottky contact controlled drain barrier. Compared to the Schottky drain structures, the new design...
In this paper, we use a novel way to research the piezoresistance coefficients of AlGaN/GaN HEFT affected by the changes of temperatures in the structure of micro-accelerometer. It is shown that saturation current of HEFT would decrease with the increasing temperature, which is about 0.028mA/°C. However, the device can work well at the temperature range of -50°C to 50°C, which indicates that it can...
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