Due to the low cost and the scaling capability of Si substrate, InAlN/GaN high-electron-mobility transistors (HEMTs) on silicon substrate have attracted more and more attentions. In this paper, a high-performance 50-nm-gate-length InAlN/GaN HEMT on Si with a high on/off current (I_on/I_off) ratio of 7.28 × 10⁶, an average subthreshold swing (SS) of 72 mV/dec, a low drain-induced barrier lowing (DIBL) of 88 mV, an off-state three-terminal breakdown voltage (BV_ds) of 36 V, a current/power gain cutoff frequency (f_T/f_max) of 140/215 GHz, and a Johnson’s figure-of-merit (JFOM) of 5.04 THz V is simultaneously demonstrated. The device extrinsic and intrinsic parameters are extracted using equivalent circuit model, which is verified by the good agreement between simulated and measuredS-parameter values. Then the scaling behavior of InAlN/GaN HEMTs on Si is predicted using the extracted extrinsic and intrinsic parameters of devices with different gate lengths (L_g). It presents that af_T/f_maxof 230/327 GHz can be achieved whenL_gscales down to 20 nm with the technology developed in the study, and an improvedf_T/f_maxof 320/535 GHz can be achieved on a 20-nm-gate-length InAlN/GaN HEMT with regrown ohmic contact technology and 30% decreased parasitic capacitance. This study confirms the feasibility of further improvement of InAlN/GaN HEMTs on Si for RF applications.

The AlGaN/GaN heterostructure field-effect transistors with different gate lengths were fabricated. Based on the chosen of the Hamiltonian of the system and the additional polarization charges, two methods to calculate PCF scattering by the scattering theory were presented. By comparing the measured and calculated source-drain resistances, the effect of the different gate lengths on the PCF scattering potential was confirmed.

This paper analyzes the velocity-field relationship of AlGaN/GaN HFETs via Monte Carlo simulation. This method is based on complete scattering mechanisms such as polarized coulomb field scattering (PCF scattering), polar optical phonon scattering, acoustic deformation potential scattering, inter-valley phonon scattering, and piezoelectric scattering. It is found that the gate bias voltage affects the PCF scattering intensity and the PCF scattering intensity influences the drift velocity under a high electric field. A decrease in peak steady-state drift velocity is observed for our fabricated AlGaN/GaN HFETs from 1.335×105 m/s at Vgs=0 V to 1.23×105 m/s at Vgs=-3 V as the gate voltage becomes more negative. When combined with the velocity-field relationship obtained from Monte Carlo simulations, the calculated current-voltage characteristics of AlGaN/GaN HFET devices are in good agreement with our experiment results. The electron saturation drift velocity deviation of AlGaN/GaN HFETs from the Monte Carlo simulation of the GaN material is attributed to the presence of PCF scattering in AlGaN/GaN HFETs. In the study, we provide strong support for the accurate modeling of AlGaN/GaN HFETs.

In this study, we proposed an enhanced mode P-GaN/AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) by combining thermal oxidation treatment of P-GaN with atomic layer deposition (OTALD) prior to gate metal deposition. Due to the thermal oxidation treatment, a smooth oxide interlayer between P-GaN and Al2O3 is formed. Compared with the device without treatment, the P-GaN gate HEMTs with OTALD present increased threshold voltage significantly from 1.8 V to 7.1 V and improved gate breakdown voltage from 18.9 V to 26.9 V. Additionally, the devices maintained a high on/off current ratio above 108 and a further improvement in off-state breakdown voltage from 1315 V to 1980 V. The record high threshold voltage and breakdown voltage make this technology promising for widespread application in P-GaN power devices.

The AlGaN/GaN heterostructure field-effect transistor (HFET) with 100 nm gate length was fabricated. An improved method is proposed to determine the value of the source access resistance corresponding to each direct current quiescent points in the saturation region of the current-voltage characteristics. The increase in the source access resistance with drain-source current has been studied, taking into account several main scattering mechanisms, including polarization Coulomb field (PCF) scattering, polar-optical-phonon scattering, piezoelectric scattering, and interface roughness scattering. It is found that PCF scattering plays a very important role in the source access resistance of AlGaN/GaN HFETs. The PCF scattering component of source access resistance decreases with the increase in drain-source current.

The surge current capability is one of the key parameters for the application of silicon carbide (SiC) Schottky barrier diode (SBD) in power converters. In this study, the surge current failure mechanism of a 650 V 4H-SiC SBD during non-repetitive surge current test is investigated. The ${I}-{V}$ measurements and microscopic observations before and after surge current failure demonstrate there are two types of failure mechanisms. Experimental and electro-thermal simulation results are combined to prove that the two different failure mechanisms originate from the varied thermal strain within the chip. This article presents the cause of surge current failure of SiC SBD and establishes a surge current failure model, which is applicable to predict and optimize the surge current capability of SiC SBD.