Amirhossein Aminbeidokhti

A Novel High-Breakdown-Voltage SOI MESFET by Modified Charge Distribution

In this paper, a novel silicon-on-insulator (SOI) metal-semiconductor field-effect transistor (MESFET) with modified charge distribution is presented. Changing charge distribution leads to lower electric field crowding and increased breakdown voltage (VBR). For modifying charge distribution, a metal region (MR) is utilized in buried oxide of the SOI MESFET. In order to achieve the best results, the MR location and dimensions are optimized carefully. DC and radio frequency characteristics of the SOI MESFET with MR (MR-SOI MESFET) are analyzed by 2-D numerical simulation and compared with conventional SOI MESFET (C-SOI MESFET) characteristics. The simulated results show that the MR has excellent effect on the VBR of the device. The VBR of the MR-SOI MESFET structure improves by 116% compared with that of the C-SOI MESFET structure. Although drain current of the proposed structure reduces slightly, 126% improvement in maximum output power density of the device is achieved due to high enhancement of the VBR. Also, the MR leads to the enhancement of maximum oscillation frequency and maximum available gain of the MR-SOI MESFET structure. As a result, the MR-SOI MESFET structure has superior electrical performances in comparison with the similar device based on the conventional structure.

High-Voltage and RF Performance of SOI MESFET Using Controlled Electric Field Distribution

A novel silicon-on-insulator metal-semiconductor field-effect transistor (SOI MESFET) with controlled electric field distribution is presented in this brief. An additional layer of oxide (LO) is located in the device channel region in order to supervise the electric field distribution. The simulation results show that the LO region has excellent effects on the breakdown voltage of the device, which increases by 50% compared with that of the conventional SOI MESFET structure. Also, the maximum output power density improves by 53%. In addition, the LO region causes the improvement of the device gains and frequency parameters. Consequently, the novel SOI MESFET structure has superior electrical characteristics compared with the similar device based on the conventional structure.

Transient-Current Method for Measurement of Active Near-Interface Oxide Traps in 4H-SiC MOS Capacitors and MOSFETs

Measurements of the near-interface oxide traps (NIOTs) aligned to the conduction band of silicon-carbide (SiC) are of particular importance as these active defects are responsible for degradation of the channel-carrier mobility in 4H-SiC MOSFETs. In this brief, a new method for measurement of the active NIOTs with energy levels aligned to the conduction band is proposed. The method utilizes transient-current measurements on 4H-SiC MOS capacitors biased in accumulation. Nitrided oxide and dry oxide are used to illustrate the applicability of the proposed measurement method.

A new double-recessed 4H-SiC MESFET with superior RF characteristics

In this article, a novel double-recessed 4H-SiC MESFET with metal plate (MP) termination technique and recessed source-drain drift region (DRMPR-MESFET) is introduced and its electrical performances are studied by two-dimensional numerical simulation. The MP modifies the electric field in the channel and modulates the surface electric field distribution that leads the further enhancement of the breakdown voltage (V BR). The recessed drift region lowers capacitances. Also it decreases total charge of the channel, lowers the electric field crowding and improves the V BR. In order to combine the advantages of the methods for achieving a high frequency and high V BR device, both of the techniques are taken into consideration together. The simulated results show that the V BR of the DRMPR-MESFET is 139 V in comparison with 120 V of the conventional double-recessed 4H-SiC MESFET with MP termination technique (CDRMP-MESFET), which does not have the recessed source-drain drift region. Also maximum oscillation frequency of the proposed structure improves significantly 267.7%. Furthermore, the maximum available gain of the DRMPR-MESFET is 13.5 dB higher than that of the CDRMP-MESFET, at 50 GHz. Therefore, the DRMPR-MESFET has superior RF performances and higher V BR, and it can be taken into consideration in high frequency and large V BR electrical performances.

A novel GaAs MESFET with multi-recessed drift region and partly p-type doped space layer

In this paper, GaAs MESFET with multi-recessed drift region and partly p-type doped space layer (MPS-MESFET) is proposed and DC and RF characteristics are analyzed by 2D numerical simulation. The multi-recesses eliminate the spaces adjacent to gate and stop the depletion region extending towards drain and source. The space layer moves the surface state out of the channel and therefore enhances the saturated drain current. Also by using a partly p-type doped space layer, the GaAs MESFET performance is further improved. As compared with conventional recessed-channel GaAs MESFET (CR-MESFET) structure, the RF simulation results show that the MPS-MESFET structure has a 3 dB gain improvement at 1 GHz. Our results show that maximum oscillation frequency of the proposed structure has increased 8.87% in comparison with the CR-MESFET structure.

Gate-Voltage Independence of Electron Mobility in Power AlGaN/GaN HEMTs

The mobility of current carriers in the channel of FETs usually depends on the applied gate voltage. This paper presents experimental evidence that the electron mobility in the 2-D electron gas under the gate of AlGaN/GaN high-electron-mobility transistors (HEMTs) is actually independent of the gate voltage. This demonstration of the gate-voltage independence of the electron mobility relates to power HEMTs, and it was achieved by introducing a new method for the mobility measurement. The gate-voltage independence of the electron mobility was observed for a wide range of temperature, from 25 °C to 300 °C. Furthermore, it is confirmed that the HEMT mobility decreases with increased temperature according to the power law (T-k) and with a quite high value of the power-law coefficient (k = 2.45).

Power-switching applications beyond silicon: The status and future prospects of SiC and GaN devices

Following a review of the key power-switch requirements and the fundamental limitations of silicon as a material, this paper describes the technical issues and the reasons that motivated the development of commercially available Schottky diodes and MOSFETs in SiC. In the second part, the paper analyzes the potential of GaN to enable further technical progress beyond the theoretical limit of Si and even significant price reduction of power-electronic switches.

Quantified Density of Active near Interface Oxide Traps in 4H-SiC MOS Capacitors

This paper presents a new method to quantify near interface oxide traps (NIOTs) that are responsible for threshold voltage instability of 4H-SiC MOSFETs. The method utilizes the shift observed in capacitance–voltage (C–V) curves of an N-type MOS capacitor. The results show that both shallow NIOTs with energy levels below the bottom of conduction band and NIOTs with energy levels above the bottom of the conduction band of SiC are responsible for the C–V shifts, and consequently, for the threshold voltage instabilities in MOSFETs. A higher density of NIOTs is measured at higher temperatures.

The Power Law of Phonon-Limited Electron Mobility in the 2-D Electron Gas of AlGaN/GaN Heterostructure

The reduction of electron mobility in AlGaN/GaN heterostructures follows the common power law, but with an unexpectedly high power coefficient. Following the experimental verification of the unusual power-coefficient value by a different measurement method, this brief presents an analysis that identifies the temperature dependence of the effective electron mass as the responsible physical mechanism for this effect. Based on this result, the measured values of electron mobility are used to calculate the effective mass of the electrons in AlGaN/GaN heterostructures over a wide temperature range, from 25 °C to 300 °C.

Dipole Type Behavior of NO Grown Oxides on 4H–SiC

In this paper, we present surprising MOS capacitor C–V bias instability observed in NO-grown oxides, with distinctly different behavior compared to that of conventional NO-annealed oxides on 4H-SiC. Using sequential back-and-forth and bias-temperature stress C–V measurements, it was demonstrated that the C–V shift direction of NO-grown oxides was opposite to that of NO-annealed oxides. A model based on bias-temperature stress orientated near-interfacial dipoles is proposed to explain this unique behavior of NO-grown oxides.