Search

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, we report on the direct-current (DC) and frequency characteristics of split-gate heterostructure field-effect transistors (HFETs) with different split-gate lengths. The split-gate HFET contains two distinct operating parts, the large and the small transconductance parts. The split-gate HFET has a current cutoff frequency ( f T ) of 814 MHz and a maximum oscillation frequency ( f max ) of 18.8 GHz in the large transconductance part. Meanwhile, in the small transconductance part, there is a higher unilateral power gain of f max = 2 7. 7 GHz. Also, the split-gate HFET exhibits a voltage gain greater than 1 (0 dB) at both DC and frequencies. Additionally, compared to the large transconductance part, the small transconductance part of the split-gate HFET presents a 53.5% reduction in DC power consumption and a larger input signal voltage range. Split-gate HFETs can be used as conventional power amplifiers in the large transconductance part and are also suitable as low-power voltage amplifiers in the small transconductance part. [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 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]

• The mechanism of current modulation in the open region of split-gate AlGaN/GaN HFETs can be explained by the fringe electric field (FEF) effect and polarization Coulomb field (PCF) scattering effect for the applied biased split-gate. • Experimental results and TCAD simulation reveal the role of the PCF scattering in split-gate AlGaN/GaN HFETs. • The PCF scattering modulates the current by affecting the mobility of the two-dimensional electron gas (2DEG) and is closely related to the additional polarization charges generated by the inverse piezoelectric effect. • This study further promotes the research and application of split-gate AlGaN/GaN HFETs. In this study, we fabricated two similar split-gate AlGaN/GaN heterostructure field-effect transistors (SG AlGaN/GaN HFETs). However, minor variations in structural design resulted in substantial differences in the current–voltage characteristics. The mechanism of current modulation in the open region of the HFET can be explained by the fringe electric field (FEF) effect and the polarization Coulomb field (PCF) scattering for the applied biased split-gate. In particular, the effects of FEF and PCF scattering on the two-dimensional electron gas in the open region were analyzed separately when only the open region was on. Experimental results and TCAD simulation reveal the role of PCF scattering in SG AlGaN/GaN HFETs and provide evidence for the universality of PCF scattering in electronic devices with the AlGaN/GaN heterostructure. This study is meaningful for the structural optimization and electrical performance enhancement of SG AlGaN/GaN HFETs. [ABSTRACT FROM AUTHOR]

Identically-sized AlGaN/GaN HFETs were fabricated on three AlGaN/GaN heterostructure with differing AlGaN barrier layer thicknesses of 15.5 nm, 19.3 nm and 24.7 nm. Based on polarization Coulomb field (PCF) scattering theory, additional polarization charges and electron mobility under the gate were calculated, and the relationship between AlGaN barrier layer thickness and P C F scattering in AlGaN/GaN H F E T s was determined. For the AlGaN/GaN H F E T s with a thicker AlGaN barrier layer, when the same gate bias was applied to the gate, the inverse piezoelectric effect (IPE) of the barrier layer was weaker, resulting in fewer additional polarization charges. The AlGaN/GaN H F E T s with a thicker AlGaN barrier layer also possessed a higher 2DEG sheet charge density, diminishing the P C F scattering intensity. It can be concluded that increasing the AlGaN barrier layer thickness reduces the IPE and raises the 2DEG sheet charge density, both of which decreases the PCF scattering intensity. The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures. • The relationship between AlGaN barrier layer thickness and polarization Coulomb field (PCF) scattering was determined. • Both of the reduce of additional polarization charges and the increase of the 2DEG density will weaken the PCF scattering. • PCF scattering intensity can be diminished by increasing the AlGaN barrier layer thickness. • The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures. [ABSTRACT FROM AUTHOR]