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This work reports on the extraction and simulation of the electron velocity–gate voltages relationship for sub-100 nm InAlN/GaN heterojunction field-effect transistors (HFETs). A peak electron velocity (ve) at an electron density (ns) of 0.41 × 1013 cm−2 was observed at 1.06 × 107 cm/s in an InAlN/GaN HFET with 60 nm gate length (Lg) by delay time analysis. The ve at a high ns of 1.5 × 1013 cm−2 was observed at 0.6 × 107 cm/s. This peak ve behavior is explained by polarization Coulomb field (PCF) scattering and optical phonon scattering based on a Monte Carlo method. As Lg scaled from 350 to 60 nm, the current gain cutoff frequency (fT) and transconductance (gm) were improved. However, the thermal performance was degraded with a bad figure of merit P150 °C. Although a weakening of the control capability of Vgs on ns (Δns/ΔVgs) was observed in the shorter Lg device, which leads to a decrease in device gm, the larger electron velocity by the increased lateral electric field (E) and the larger Δve/ΔVgs by the increased PCF scattering still enhance the peak gm. Results indicate that the enhancement of Δve/ΔVgs is a vital method to strengthen the modulation of the gate on current and to suppress the short channel effect in GaN HFET. Our work supports a deeper understanding and analysis of sub-100 nm InAlN/GaN HFET device performance and physical mechanisms. [ABSTRACT FROM AUTHOR]

Capture and, subsequently, in situ characterization of microparticles generally require complex fabrication processes and sophisticated techniques in microfluidic devices. In this paper, we present a simple and inexpensive technique for capturing and applying chemical agents to individual charged microparticles with the same glass microelectrode in a circular microfluidic channel. The microfluidic device features a thin poly-dimethyl-siloxane (PDMS) layer (100 µm, thickness) above the circular channel (diameter, 50 µm) so that the tip of the glass microelectrode can enter into the channel by penetrating through the thin PDMS layer. When an electric field is applied across the tip of the microelectrodes, the tip can capture charged microparticles or living cells that are flowing through the channel. Meanwhile, the same glass microelectrode can be used to apply chemical agents to the captured particles or living cells by filling the solution of the chemical agent into its tip. This simple design method offered simple fabrication without the need for any specialized equipment for the manipulation of charged particles or living cells in controlled microenvironments. [ABSTRACT FROM AUTHOR]

In this study, GaN-based side-gate heterostructure transistors (SGHTs) with two electrical operating modes were fabricated. In the first operating mode, the SGHT was utilized as a common-source voltage amplifier with low power consumption and a broad input signal range. Analysis of the main scattering mechanisms affecting the electrical transport of two-dimensional electron gas (2DEG) in the channel revealed that polar optical phonon scattering and polarization Coulomb field (PCF) scattering play dominant roles under different side-gate voltages. In addition, channel current modulation of 2DEG electron mobility is primarily attributed to PCF scattering. Due to PCF scattering, the channel width also modulates the threshold voltage in this mode of operation. Moreover, in the second operating mode, the SGHT functioned as a traditional GaN high electron mobility transistor, allowing for electrically modulated threshold voltage and transconductance. [ABSTRACT FROM AUTHOR]

This paper demonstrates the improvement of device linearity in AlGaN/GaN heterostructure field effect transistors (HFETs) using polarization Coulomb field (PCF) scattering and investigates the relationship between device linearity and PCF scattering under 10 and 20 V drain bias. The mobility of the gate-to-source region in AlGaN/GaN HFETs is calculated using the Monte Carlo method. We find that PCF scattering decreases with an increase in gate bias (from −3 to −0.5 V) under high field conditions, leading to lower gate-to-source resistance. Under 20 V drain bias, linearity is worse than under 10 V drain bias. The transconductance drop is significant in AlGaN/GaN HFETs, which damages linearity. By adopting an appropriate drain bias, PCF scattering can alleviate transconductance drop and improve the linearity of AlGaN/GaN HFETs. [ABSTRACT FROM AUTHOR]

In our case, the pulsed wire method is applied to the magnetic field measurement of the permanent magnets in focusing device of millimeter-wave traveling wave tube (TWT). The focusing device using permanent magnets is used to help the electron beam keep shape and make it possible go through the slow-wave circuit, effectively interact with the microwave field and well received by collectors, which makes the measurement become a key factor for the development of the millimeter-wave TWT technique. Furthermore, the wire method can be extended used to magnetic field measurement of the magnet with small via hole. The pulsed wire technique is based on the excitation of the harmonics of a wire vibration by Lorenz forces between current in a wire and the surrounding magnetic field. Knowing the amplitude and the phase of the various harmonics of the wire vibration, one can easily reconstruct the surrounding magnetic field. As sensitive the wire system is, ultrastable supporters, high accurate mechanical adjusters, precise light and electric centering device are installed and relevant parameters are properly chosen. In addition, shorter wire is used to reduce the sag, and a simple and effective wire-position detector providing accuracy up to 1 μm is designed and tested. Experiment confirms the theoretical conclusions and shows a positive future of application. The prototype system can show several relevant results, e.g., three-dimensional magnetic intensity distribution, maximum, minimum, and medium magnetic inductions, pole pitch error, etc. [ABSTRACT FROM AUTHOR]

In this study, a split-gate AlGaN/GaN heterostructure field-effect transistor with an auxiliary gate was fabricated. Through experiment and analysis, it was discovered that by applying a constant potential (usually 0 V or negative potential) to the auxiliary gate, a negative bias can be formed between the auxiliary gate and the channel. This consumes the two-dimensional electron gas in the channel, leading to significant improvements in the saturation characteristics of split-gate devices. By applying different potentials to the main gate and the auxiliary gate, a variety of device working modes can be obtained, and the threshold voltage can be altered across a large range. These advantages make split-gate devices with auxiliary gates more suitable for increasingly complex integrated circuit applications. [ABSTRACT FROM AUTHOR]