Abstract-Terahertz monolithic integrated waveguide transmission lines based on wide bandgap semiconductor materials

Journal of Applied Physics

Yang Li, Xiao-Hua Ma, Lin-An Yang, Jin-Ping Ao, Yue Hao,

Geometry of the TMIW-TL and the TMIW-GCPW transitions based on the SiC substrate: (a) ideal model and (b) actual model.

https://aip.scitation.org/doi/10.1063/1.5083097

In this paper, terahertz monolithic integrated waveguide (TMIW) transmission lines (TLs) are analyzed and fabricated based on wide bandgap semiconductor materials. The ignored parameters of TLs at low frequencies, such as the via-hole shape, the titanium/gold thickness and roughness, and the micropipe effect of material, are especially investigated based on the semiconductor fabrication technique and the terahertz-wave theory. Subsequently, the fine optimized TMIW-TL and the transition to grounded coplanar waveguide are fabricated. The measurement shows that the attenuation constant of a TL is as low as 0.19 dB/λg at 220 GHz. The proposed TMIW can provide electrical performance similar to the conventional air-filled waveguide, while it has only 10% of the volume, which indicates a great potential for future terahertz integrated systems.

Abstract-Enhancement of Negative Differential Mobility Effect in Recessed Barrier Layer AlGaN/GaN HEMT for Terahertz Applications

Hongliang Zhao. Lin-An Yang, Hao Zou, Xiao-hua Ma, Yue Hao

https://ieeexplore.ieee.org/document/8634873

A recessed barrier layer (RBL) structure is proposed in the micrometer-sized AlGaN/GaN high-electron mobility transistor (HEMT) for terahertz applications. It is found by using numerical simulation that the properly designed RBL structure can trigger the formation and propagation of electron domains in the 2-D electron gas (2-DEG) channel. As a result, the fundamental frequency can be extended even up to terahertz regime, and also it can be tuned in a certain range by the bias voltage of Schottky contact gate that acts as a hot-electron injector just like the notch-doped Gunn diode. Our simulations show that the 0.3-μm -gate HEMT with the RBL structure having the depth of 10–15 nm and the length of 200–400 nm can generate the stable and tunable oscillations in the range of around 0.8–1.6 THz under the normally gate bias of −0.2–0.4 V, as well as the ratio of RF-to-dc current component ranging from 3.04% to 7.2%. These available characteristics come from the redistribution of electric field in the 2-DEG channel. Compared with the ungated and the top-gated planar Gunn diodes ever reported, the proposed RBL structural AlGaN/GaN HEMT can be easily fabricated and operated under normal conditions, demonstrating a great potential application in terahertz radiation sources.

Abstract-Thermal Modeling of the GaN-based Gunn Diode at Terahertz Frequencies

Ying Wang,  Jinping Ao,  Shibin Liu,  Yue Hao,

https://www.mdpi.com/2076-3417/9/1/75

In this paper, a comprehensive evaluation of thermal behavior of the GaN vertical n⁺-n⁻-n-n⁺ Gunn diode have been carried out through simulation method. We explore the complex effects of various parameters on the device thermal performance through a microscopic analysis of electron movements. These parameters include operation bias, doping level, and length of the active region. The increase of these parameters aggravates the self-heating effect and degrades the electron domains, which therefore reduces the overall performance output of the diode. However, appropriate increase of the doping level of active region makes the lattice heat distribute more uniformly and improves the device performance. For the first time, we propose the transition domain, which is in between the dipole domain and accumulation layer, and stands for the degradation of the electron domain. We have also demonstrated that dual domains occur in the device with longer active region length and higher doping level under EB (Energy balance) model, which enhances the harmonics component. Electric and thermal behaviors analysis of GaN vertical Gunn diode makes it possible to optimize the device.

Abstract-Engineering rainbow trapping and releasing in ultrathin THz plasmonic graded metallic grating strip with thermo-optic material

Yan Liu, Yibo Wang, Genquan Han, Yao Shao, Cizhe Fang, Siqing Zhang, Yan Huang, Jincheng Zhang, and Yue Hao

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-2-1278&origin=search

In this paper, we propose an ultrathin THz plasmonic metallic strip based on graded grating structure with thermo-optic material, which exhibits a strong engineering of trapping and releasing electromagnetic waves in terahertz regimes. The dispersion properties of the ultrathin spoof slow-wave plasmonic graded grating waveguide are characterized using the finite element method, and the propagation characteristics of the grating structures are thoroughly analyzed by the dispersion curves, electric field magnitude distribution, and electric field vertical distribution. The gradient grating waveguide is demonstrated to be an ideal slow-wave system for trapping and releasing surface plasmon polaritons (SPPs) waves through tuning the refractive index of the thermo-optic material. The reflected location for the SPPs waves on the graded corrugated metal strip at 1.1 THz at different temperatures are compared. It is proved that such ultrathin gradient grating waveguide provides an excellent performance for trapping and releasing surface waves at THz, which permits applications for future optical communications.

© 2017 Optical Society of America

Abstract-Design of 3D filtering antenna for the application of terahertz

•  Yang Li ¹ ; Lin-an Yang ¹ ; Shao-bo Wang ¹ ; Lin Du ¹ ; Yue Hao ¹
• 
  
http://digital-library.theiet.org/content/journals/10.1049/el.2016.3808

• 
  
• Affiliations: 1: The State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, People's Republic of China 

A new terahertz (THz) filtering antenna realised by 3D substrate integrated circular waveguide (3D-SICW) is presented. The filtering antenna is designed on a low-temperature co-fired ceramic substrate. Different from traditional planar structure, the direction of power in 3D-SICW is along Z-axis and this will significantly enhance the performance of the devices at THz frequency. The filtering antenna is constructed by two 3D-SICW cavities and a standard substrate integrated waveguide (SIW) cavity, where one SICW cavity and the standard SIW cavity form the bandpass filter by using electric coupling and the other SICW cavity is used as antenna. The results indicate that the passband of filtering antenna range from 170.4 to 177.8 GHz and the gain of antenna is about 5.7 dB. Finally, the filtering antenna is fabricated and measured to verify the simulation prediction. The measured and simulated results are in good agreement at such high frequency

Abstract-Spoof surface plasmon polaritons based on ultrathin corrugated metallic grooves at terahertz frequency

Yan Liu, Jing Yan, Yao Shao, Jie Pan, Chunfu Zhang, Yue Hao, and Genquan Han
https://www.osapublishing.org/ao/abstract.cfm?uri=ao-55-7-1720

We investigate the dispersion properties of an ultrathin spoof plasmonic waveguide based on metal strip grooves using the finite element method. The confinement ability of the surface plasmon polariton (SPP) waves are influenced by the dispersion curves, which can be modulated by the structure parameters. The propagation characteristics of a subwavelength planar plasmonic waveguide ring resonator have also been studied. Furthermore, a gain medium is introduced to compensate for the propagation loss of the SPP wave in the device at terahertz frequency. It is demonstrated that the gain medium provides an enhancement for the control of on/off states of the signal with the presence of pumping, which paves a way for gain-assisted switching and lasing applications in the terahertz regime.

© 2016 Optical Society of America

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Abstract-Dislocation blocking by AlGaN hot electron injecting layer in the epitaxial growth of GaN terahertz Gunn diode

Liang Li, Lin'an Yang, Jincheng Zhang, and Yue Hao

State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, China 

http://jap.aip.org/resource/1/japiau/v114/i10/p104508_s1?isAuthorized=no

This paper reports an efficient method to improve the crystal quality of GaN Gunn diode with AlGaN hot electron injecting layer (HEI). An evident reduction of screw dislocation and edge dislocation densities is achieved by the strain management and the enhanced lateral growth in high temperature grown AlGaN HEI layer. Compared with the top hot electron injecting layer (THEI) structure, the bottom hot electron injecting layer (BHEI) structure enhances the crystal quality of transit region due to the growth sequence modulation of HEI layer. A high Hall mobility of 2934 cm²/Vs at 77 K, a nearly flat downtrend of Hall mobility at the temperature ranging from 300 to 573 K, a low intensity of ratio of yellow luminescence band to band edge emission, a narrow band edge emission line-width, and a smooth surface morphology are observed for the BHEI structural epitaxy of Gunn diode, which indicates that AlGaN BHEI structure is a promising candidate for fabrication of GaN Gunn diodes in terahertz regime.

© 2013 AIP Publishing LLC

Article Outline

1. INTRODUCTION
2. EPITAXIAL GROWTH
3. MEASUREMENTS AND DISCUSSIONS
   1. TEM characterization
   2. HRXRD characterization
   3. High/low temperature-dependent Hall characterization
   4. PL characterization
   5. AFM characterization
4. CONCLUSION