A novel small-signal equivalent circuit model for GaN HEMTs incorporating a dual-field-plate

An accurate and novel small-signal equivalent circuit model for GaN high-electron-mobility transistors(HEMTs)is proposed,which considers a dual-field-plate(FP)made up of a gate-FP and a source-FP.The equivalent circuit of the overall model is composed of parasitic elements,intrinsic transistors,gate-FP,and source-FP networks.The equivalent circuit of the gate-FP is identical to that of the intrinsic transistor.In order to simplify the complexity of the model,a series combination of a resistor and a capacitor is employed to represent the source-FP.The analytical extraction procedure of the model parameters is presented based on the proposed equivalent circuit.The verification is carried out on a 4×250μm GaN HEMT device with a gate-FP and a source-FP in a 0.45μm technology.Compared with the classic model,the proposed novel small-signal model shows closer agreement with measured S-parameters in the range of 1.0 to 18.0 GHz.

Simulation research on offset field-plate used as edge termination in 4H-SiC merged PiN-Schottky diodes

A new structure of 4H-silicon carbide （SIC） merged PiN-Schottky （MPS） diodes with offset field-plate （FP） as edge termination is developed. To understand the influences of 4H-SiC MPS diodes with offset FP on the characteristics, simulations have been done by using ISE TCAD. Related factors of offset FP have been studied as well to optimise the reverse characteristics of 4H SiC MPS diodes. The simulation results show that the device using offset FP can create a higher blocking voltage under reverse bias as compared with that using field guard rings. Besides, the offset FP does not cause any extra steps in the manufacture of MPS diodes.

A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor

In this paper, we present a two-dimensional （2D） fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor （FP-HEMT） on the basis of 2D Poisson＇s solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, A1GaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco-Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc.

Development and characteristic analysis of a field-plated Al_2O_3 /AlInN/GaN MOS-HEMT

We present an AIInN/AlN/GaN MOS-HEMT with a 3 nm ultra-thin atomic layer deposition （ALD） Al2O3 dielectric layer and a 0.3 μm field-plate （FP）-MOS-HEMT. Compared with a conventional AIInN/AlN/GaN HEMT （HEMT） with the same dimensions, a FP-MOS-HEMT with a 0.6 μm gate length exhibits an improved maximum drain current of 1141 mA/mm, an improved peak extrinsic transconductance of 325 mS/mm and effective suppression of gate leakage in both the reverse direction （by about one order of magnitude） and the forward direction （by more than two orders of magnitude）. Moreover, the peak extrinsic transconductance of the FP-MOS-HEMT is slightly larger than that of the HEMT, indicating an exciting improvement of transconductance performance. The sharp transition from depletion to accumulation in the capacitance-voltage （C-V） curve of the FP-MOS-HEMT demonstrates a high-quality interface of Al2O3/AlInN. In addition, a large off-state breakdown voltage of 133 V, a high field-plate efficiency of 170V/#m and a negligible double-pulse current collapse is achieved in the FP-MOS-HEMT. This is attributed to the adoption of an ultra-thin Al2O3 gate dielectric and also of a field-plate on the dielectric of an appropriate thickness. The results show a great potential application of the ultra-thin ALD-Al2O3 FP-MOS-HEMT to deliver high currents and power densities in high power microwave technologies.

Analysis of the modulation mechanisms of the electric field and breakdown performance in AlGaN/GaN HEMT with a T-shaped field-plate

A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP） is composed of a source-connected field-plate （S-FP） and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP （S-FP HEMT） shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.

X波段AlGaN/GaN HEMTs Γ栅场板结构研究(英文)

基于SiC衬底成功研制X波段0.25μm栅长带有Γ栅场板结构的AlGaN/GaN HEMT,对比T型栅结构器件,研究了Γ栅场板引入对器件直流、小信号及微波功率特性的影响。结果表明,Γ栅场板结构减小器件截止频率及振荡频率,但明显改善器件膝点电压和输出功率密度。针对场板长度分别为0.4、0.7、0.9、1.1μm,得出一定范围内增加场板长度,器件输出功率大幅度提高,并结合器件小信号模型提参结果分析原因。在频率8 GHz下,总栅宽1 mm,场板长度0.9μm的器件,连续波输出功率密度7.11 W/mm,功率附加效率(PAE)35.31%,相应线性增益10.25 dB。