This letter reports undoped AlGaN/GaN high-electron-mobility transistors (HEMTs) fabricated with a Si-CMOS-compatible technology based on Ti/Al/W ohmic and Schottky contacts. The use of ohmic recess is key to reduce the contact resistance of this Au-free metallization below 0.5 Ω·mm. Comparison of HEMTs fabricated on the same wafer with and without ohmic recess shows that the recess provides a tenfold reduction in contact resistance, resulting in a fivefold lower forward voltage drop at IDS = 100 mA/mm. The reported Au-free AlGaN/GaN HEMT fabrication technology provides similar performance (i.e., contact resistance, leakage current, and breakdown voltage) than state-of-the-art Au-based AlGaN/GaN HEMTs and can be used in standard Si fabs without the risk of contamination.

AlGaN/GaN High-Electron-Mobility Transistors Fabricated Through a Au-Free Technology

Porous 3C-SiC (pSiC) samples with different pore diameters were prepared from polycrystalline n-type 3C-SiC films by electrochemical anodization using a mixture of HF and ethanol as the electrolyte solution. The pSiC surface was chemically modified via the sputtering of Pd and Pt nanoparticles as a hydrogen catalyst. Changes in the resistance were monitored with respect to hydrogen concentrations in the range of 110–410 ppm. The variations in the electrical resistance at the presence of nitrogen diluted with hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen. Regardless of the catalyst, the 25 nm pore diameter samples exhibited better response and recovery properties than the 60 nm pore diameter samples. It was found that the pore size affects the catalyst reaction and results in changes in the response factor to hydrogen. A large change in resistivity was observed with the Pd catalyst and the hydrogen sensing performance improved at high temperatures.

Characterization of porous cubic silicon carbide deposited with Pd and Pt nanoparticles as a hydrogen sensor

A critical review of AlGaN/GaN-heterostructure based Schottky diode/HEMT hydrogen (H2) sensors for aerospace and industrial applications

An AlGaN/GaN Schottky diode is fabricated using an Au free process. Both ohmic and Schottky contact are studied. The ohmic contact results show low contact resistance and good surface morphology. The specific resistance (ρc) and contact resistance (Rc) of the ohmic contact are ~ 3.5×10-5 Ω×cm2 and 2.1 Ω·mm, respectively. Several current transport mechanisms are employed to analyze the measured I- V curves of the diode. The data have demonstrated that at a lower forward bias the combination of generation recombination and tunneling current mechanisms are dominant, whereas the thermionic emission mechanism becomes more significant at a higher forward bias. The effective Schottky barrier height is estimated to be 0.99 eV. The breakdown voltage of AlGaN/GaN Schottky diode is ~ 125 V.

AlGaN/GaN Schottky Diode Fabricated by Au Free Process

Hydrogen gas sensors are important because of the significant use of hydrogen in industrial and commercial applications. In this study, we synthesized a novel CsxWO3/MoS2 nanocomposite using a solvothermal method. The samples were spin-coated on Si/SiO2 substrates, and the sensors were fabricated with interdigital electrodes. The hydrogen gas sensing properties of the sensor were investigated. CsxWO3/MoS2 exhibited an outstanding hydrogen gas sensing ability at room temperature. In particular, the nanocomposite comprising 15 wt.% MoS2 (15% CsxWO3/MoS2) showed a 51% response to hydrogen gas at room temperature. Further, it exhibited an excellent cyclic stability for hydrogen gas sensing, which is crucial for practical applications. Therefore, this study facilitates the development of effective and efficient hydrogen gas sensors operable at room temperature.

https://www.frontiersin.org/articles/10.3389/fmats.2022.831725/pdf

Highly Efficient MoS2/CsxWO3 Nanocomposite Hydrogen Gas Sensors

The response of Pt-circular Schottky diodes fabricated on undoped AlGaN/GaN high-electron-mobility-transistor (HEMT) structure to hydrogen gas at various temperatures, ranging from 25°C to 200°C has been investigated. A 5 nm-thick of catalytic Pt Shottky contact is formed by electron beam evaporation. Both forward and reverse currents of the device increase upon exposing to hydrogen gas. Although a slight change of forward and reverse current is obtained at room temperature upon exposure to hydrogen but both currents drastically increase with the increase of temperatures. The time-transient characteristics show the average current increment and decrement speed of 27.6 nA/sec and 17.6 nA/sec, respectively at constant forward bias of 1V and temperature of 200°C.

The Sensing Performance of Hydrogen Gas Sensor Utilizing Undoped-AlGaN/GaN HEMT

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The Sensing Performance of Hydrogen Gas Sensor Utilizing Undoped-AlGaN/GaN HEMT