In this letter, we demonstrate a novel PEALD-AlN/LPCVD-Si3N4 dual gate dielectric employed in enhancement-mode GaN MISFETs, where the gate recess is fabricated based on our proposed self-terminating gate recess etching technique using GaN cap layer as recess mask. By using LPCVD-Si3N4 and PEALD-AlN dual gate dielectric layer, the devices exhibit a high quality gate dielectric and a good GaN channel interface, yielding a high gate swing up to 18V and a high channel effective mobility of 137 cm2/V·s at such high gate bias. Thus, the fabricated devices feature a high maximum drain current density of 823 mA/mm, a threshold voltage of 2.6 V, an on-resistance of 7.4 Ω·mm, and an ON/OFF current ratio of 108 with gate-drain distance of 2 μm. Meanwhile, a high OFF-state breakdown voltage of 1290 V is achieved with 10 μm gate-drain distance. The corresponding specific on-resistance is as low as 1.76 mΩ·cm2, leading to a high Baliga’s figure of merit of 945 MW/cm2.

With the development of Through Silicon Vias (TSV) and Re-distributed Layer (RDL) manufacturing technology, it is applied to high-frequency and high-speed data path interconnection. Compared with traditional direct current (DC) supply, it pays more attention to transmission performance deteriorates at high frequencies. Designs without consideration of the high-frequency effects of TSV and RDL will seriously affect signal integrity and cause significant performance degradation on high-speed channels. In this paper, the frequency-dependent transmission characteristics of the TSV and RDL are investigated. Three test vehicles were designed for frequency-domain measurement and verification. The TRL de-embedding process is introduced to obtain the accurate S parameters of the TSV-RDL Coplanar Waveguide (CPW). Accordingly, an equivalent-circuit model is constructed to study the impact of RLGC parameters on transmission loss from DC to high frequency up to 40 GHz , which exhibits a good correlation with the measured and de-embedded transmission characteristics results. It found that the crucial effect of oxide-layer capacitance ( C_ox ) in the low-frequency range (from 100 kHz to 1 GHz ), while conductance and capacitance in silicon ( C_si and G_si ) have a vital impact in the mid-frequency range (from 1 GHz to 10 GHz). Additionally, the inductance ( L ) component is found to have a dominant impact on the transmission loss in the high-frequency range (from 10 GHz to 40 GHz ).

The harsh electromagnetic environment poses a threat to the reliability and safe operation of Gallium nitride (GaN) radio frequency and microwave high-electron-mobility transistors (HEMTs). In this work, we experimentally investigate the thermo-electro multiphysics coupling failure of GaN HEMTs under high-power microwave (HPM) pulse stress. A transient thermal response test and surface electric field distribution measurement methods of GaN HEMTs under HPM stress were proposed. This study demonstrates that at low power HPM injection, the peak temperature of 51 °C is located at the gate–drain access region near the gate side. As the HPM injection power approaches the destruction threshold level, an obvious hot spot of 64 °C is found however strangely in the gate–source access region at the gate edge, in the vicinity of the gate bond pad, or in other words, the input end of the microwave signals. The damage spot is exactly sitting on the hot spot, and also overlapping with the electric field concentration observed by the electric field scanning. This means it is the thermo-electro multiphysics coupling but not solely the thermal burnout that causes the device failure under HPM pulse stress. These findings are of great significance for predicting damage location and improving the reliability design against the complex electromagnetic environments.

In this study, a high-sensitivity composite probe capable of simultaneously measuring electric- and magnetic-field components is presented. The composite probe contains a U-shaped loop, two parasitic long loops, and a pair of strip-lines as a transmission part. First, the U-shaped loop is designed to test both electric- and magnetic-field. Second, two parasitic long loops are placed at both sides of the U-shaped loop to increase the sensitivity. Third, to characterize and calibrate the probe, a standard microstrip line is manufactured and used. Finally, the proposed probe is printed and tested to prove the feasibility of the design. The tested results indicate that the proposed probe can not only simultaneously test electric- and magnetic-fields, but also have a wider working bandwidth and higher sensitivity

Chiral amino alcohols are prevalent synthons in pharmaceuticals and synthetic bioactive compounds. The efficient synthesis of chiral amino alcohols using ammonia as the sole amino donor under mild conditions is highly desired and challenging in organic chemistry and biotechnology. Our previous work explored a panel of engineered amine dehydrogenases (AmDHs) derived from amino acid dehydrogenase (AADH), enabling the one-step synthesis of chiral amino alcohols via the asymmetric reductive amination of α-hydroxy ketones. Although the AmDH-directed asymmetric reduction is in a high stereoselective manner, the activity is yet fully excavated. Herein, an engineered AmDH derived from a leucine dehydrogenase from Sporosarcina psychrophila (SpAmDH) was recruited as the starting enzyme, and the combinatorial active-site saturation test/iterative saturation mutagenesis (CAST/ISM) strategy was applied to improve the activity. After three rounds of mutagenesis in an iterative fashion, the best variant wh84 was obtained and proved to be effective in the asymmetric reductive amination of 1-hydroxy-2-butanone with 4-fold improvements in k_cat/K_m and total turnover number (TTN) values compared to those of the starting enzyme, while maintaining high enantioselectivity (ee >99%) and thermostability (T₅₀¹⁵ >53°C). In preparative-scale reaction, the conversion of 100 and 200 mM 1-hydroxy-2-butanone catalyzed by wh84 was up to 91–99%. Insights into the source of an enhanced activity were gained by the computational analysis. Our work expands the catalytic repertoire and toolbox of AmDHs.

Traditional GaAs-based frequency multipliers still exhibit great challenges to meet the demand for solid-state high-power THz sources due to low breakdown voltage and heat dissipation of the Schottky barrier diode (SBD). In this study, a GaN SBD chain was fabricated with n⁻/n⁺-GaN structure. As a consequence, the breakdown voltage of 54.9 V at 1 μA and cut-off frequency of 587.5 GHz at zero bias were obtained. A 120 GHz frequency-doubler module based on the GaN SBD chain was designed and fabricated. When driven with 500 mW input power in a continuous wave, the output power of the frequency-doubler module was 15.1 mW at 120 GHz. Moreover, the experiments show that the frequency-doubler module can endure an input power of 2 W. In addition, it is worth noting that the SBD chain works well at an anode temperature of 337.2 °C.