A 2-D simulation of off-state breakdown voltage (V_BD) for AlGaN/GaN high electron mobility transistors (HEMTs) with multi field-plates (FPs) is presented in this paper. The effect of geometrical variables of FP and insulator layer on electric field distribution and V_BD are investigated systematically. The FPs can modulate the potential lines and distribution of an electric field, and the insulator layer would influence the modulation effect of FPs. In addition, we designed a structure of HEMT which simultaneously contains gate FP, source FP and drain FP. It is found that the V_BD of AlGaN/GaN HEMTs can be improved greatly with the corporation of gate FP, source FP and drain FP. We achieved the highest V_BD in the HEMT contained with three FPs by optimizing the structural parameters including length of FPs, thickness of FPs, and insulator layer. For HEMT with three FPs, FP-S alleviates the concentration of the electric field more effectively. When the length of the source FP is 24 μm and the insulator thickness between the FP-S and the AlGaN surface is 1950 nm, corresponding to the average electric field of about 3 MV/cm at the channel, V_BD reaches 2200 V. More importantly, the 2D simulation model is based on a real HMET device and will provide guidance for the design of a practical device.

To solve the time-consuming, laborious, and inefficient problems of traditional methods using classical optimization algorithms combined with electromagnetic simulation software to design antennas, an efficient design method of the multi-objective antenna is proposed based on the multi-strategy improved sparrow search algorithm (MISSA) to optimize a BP neural network. Three strategies, namely Bernoulli chaotic mapping, inertial weights, and t-distribution, are introduced into the sparrow search algorithm to improve its convergent speed and accuracy. Using the Bernoulli chaotic map to process the population of sparrows to enhance its population richness, the weight is introduced into the updated position of the sparrow to improve its search ability. The adaptive t-distribution is used to interfere and mutate some individual sparrows to make the algorithm reach the optimal solution more quickly. The initial parameters of the BP neural network were optimized using the improved sparrow search algorithm to obtain the optimized MISSA-BP antenna surrogate model. This model is combined with multi-objective particle swarm optimization (MOPSO) to solve the design problem of the multi-objective antenna and verified by a triple-frequency antenna. The simulated results show that this method can predict the performance of the antennas more accurately and can also design the multi-objective antenna that meets the requirements. The practicality of the method is further verified by producing a real antenna.

A comprehensive model for 2DEG characteristics of In_xAl_1−xN/AlN/GaN heterostructure has been presented, taking both polarization and bulk ionized charge into account. Investigations on the 2DEG density and electron distribution across the heterostructure have been carried out using solutions of coupled 1-D Schrödinger-Poisson equations solved by an improved iterative scheme. The proposed model extends a previous approach allowing for estimating the quantum mechanical effect for a generic InAlN/GaN-based HEMT within the range of the Hartree approximation. A critical AlN thickness (~2.28 nm) is predicted when considering the 2DEG density in dependence on a lattice matched In_0.17Al_0.83N thickness. The obtained results present in this work provide a guideline for the experimental observation of the subband structure of InAlN/GaN heterostructure and may be used as a design tool for the optimization of that epilayer structure.

We present a high-performance AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrate with novel stacked passivation layer (HfO2/SiO2). The stacked passivation structure can effectively modulate the electric field and reduce the electric field peak on the gate side, thus improving the breakdown voltage of the device. The prepared device with a gate length of 450 nm has a unit current gain cutoff frequency (fT) of 31.5 GHz, a maximum oscillation frequency (fMAX) of 46.3 GHz, and a three-terminal OFF-state breakdown voltage (BVgd) of 140 V at the gate-drain distance of 2.3 μm. The estimated Johnsonfs figure of merit (J-FOM=BVgd×fT) is 4.4 THz∙V, which is three and five times higher than that of the device with single HfO2 passivation layer and single SiO2 passivation layer, respectively. Furthermore, a significant suppression of the current collapse ( 5.7%) is observed due to the electric field redistribution near the drain region. The results show that the AlGaN/GaN HEMTs with stacked passivation layer proved to be a promising candidate for high-performance radio frequency (RF) power device applications.

We propose a high temperature annealing process in N ₂ ambience after N ₂ O plasma treatment for AlGaN/GaN HEMT. The annealing process effectively improves the plasma treated surface condition and decreases the current collapse from 41.7% to 10.6%. The N ₂ O plasma treatment is performed in a PECVD chamber and the followed high temperature annealing process is carried out at 800°C for 20min in rapid temperature annealing (RTA) system. Compared to the devices with only N ₂ O plasma treatment, the devices with an extra high temperature annealing process perform lower surface state density (2.51E+12 cm ⁻² eV ⁻¹ , $\boldsymbol{\Delta }\text{E}$ from 0.353 eV to 0.413 eV; 5.38E+11 cm ⁻² , $\boldsymbol{\Delta }\text{E}$ > 0.519 eV) and better dynamic characteristics.

in this study, we report a novel approach for achieving high-performance enhancement mode (E-mode) InAlN/GaN MOS HEMTs based on the fluorine treatment and a p-type NiOx gate (F-NiO HEMT). The NiO film was deposited at different substrate temperatures using reactive sputtering in a varied mixture of O2 and Ar. We show that the threshold voltage (VTH) is effectively modulated by comprehensively optimizing fluorine ion implantation and NiO sputtering conditions without requiring gate recess etching. The influence of different NiO deposition conditions on electrical properties and the critical interface of NiOx/InAlN have been investigated in detail. The proposed E-mode F-NiO HEMT exhibits superior on-state characteristics, including more positive VTH, enhanced gate voltage swing, larger transconductance gm and also superior gate control over the channel. The dual C-V and pulsed mode measurements confirm the excellent NiOx/AlInN interface and effective suppression of current collapse. We propose a model to explain the contrasting temperature-dependent coefficients of VTH shifts observed in pure fluorine ion-implanted and NiO-based devices. The underlying mechanisms at elevated temperatures are also analyzed.