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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]

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]