Query: β-Ga2O3 MOSFETs for radio frequency operation 

Candidate papers:

abstract: In this Letter, we present direct current (DC) small signal radio frequency (RF) and large signals with pulsed and continuous wave (CW) studies and characterization on oxygen annealed (OA) b Ga2O3 metal oxide semiconductor field effect transistors (MOSFETs) with significantly improved CW output power density (Pout) when compared to other b Ga2O3 RF devices. The OA process is found to be useful in compensating and neutralizing the donors in the unintentionally doped (UID) buffer layer and, hence, suppressing a second depletion effect in this UID layer. The device demonstrates a peak DC drain current of 200 mA/mm, a transconductance of 11 mS/mm, and an on/off ratio of 109. Small signal RF characterization indicates a cut off frequency and maximum oscillation frequency (fT/fmax) of 1.8 GHz and 4.2 GHz, respectively. The device also shows an output power (Pout)/peak power added efficiency (PAE)/gain of 0.4 W/mm/10%/3.2 dB and 0.43 W/mm/12%/3.6 dB for CW and pulsed signals, respectively, at an operation frequency of 1 GHz.
author_names: Yuanjie Lv

Xingchang Fu

Yanni Zhang

Pengfei Dong

Hanghai Du

Shixiong Liang

Tingting Han

Jincheng Zhang

Zhihong Feng

Hui Zhou

Shujun Cai

Yue Hao
title: Oxygen annealing impact on b Ga2O3 MOSFETs: Improved pinch off characteristic and output power density
year: 2020

abstract: We demonstrate a <inline formula> <tex math notation="LaTeX"\beta /tex math>/inline formula> Ga<sub>2</sub>O<sub>3</sub> MOSFET with record high transconductance <inline formula> <tex math notation="LaTeX"{g}_{m} /tex math>/inline formula> of 21 mS/mm and extrinsic cutoff frequency <inline formula> <tex math notation="LaTeX"{f}_{T} /tex math>/inline formula> and maximum oscillating frequency <inline formula> <tex math notation="LaTeX"{f}_{\max /tex math>/inline formula> of 3.3 and 12.9 GHz, respectively, enabled by implementing a new highly doped ohmic cap layer with a sub micron gate recess process. RF performance was further verified by CW Class A power measurements with passive source and load tuning at 800 MHz, resulting in <inline formula> <tex math notation="LaTeX"{P}_{{OUT} /tex math>/inline formula> power gain, and power added efficiency of 0.23 W/mm, 5.1 dB, and 6.3% respectively. These preliminary results indicate potential for monolithic or heterogeneous integration of power switch and RF devices using <inline formula> <tex math notation="LaTeX"\beta /tex math>/inline formula> Ga<sub>2</sub>O<sub>3</sub>
author_names: Andrew J Green

Kelson D Chabak

Michele Baldini

Neil A Moser

Ryan Gilbert

Robert C Fitch

Gunter P Wagner

Zbigniew Galazka

J P McCandless

Antonio Crespo

Kevin D Leedy

Gregg H Jessen
title: \beta$ Ga2O3 MOSFETs for Radio Frequency Operation
venue: IEEE Electron Device Letters
year: 2017

abstract: b Ga2O3 metal oxide semiconductor field effect transistors (MOSFETs) with gate lengths (Lg) of 50 1000 nm were fabricated, employing a thin channel layer formed by a shallow Si ion implantation doping to maintain a high aspect ratio between an Lg and a gate to channel distance. The MOSFETs with Lg 200 nm had a maximum drain current density of about 250 mA/mm and a peak extrinsic transconductance of 17 mS/mm. The short channel effect was well suppressed for the devices with Lg =200 nm, leading to excellent RF device characteristics represented by a record maximum oscillation frequency of 27 GHz at Lg 200 nm. From simple delay time analysis on the MOSFETs, the effective electron velocity passing through a region under the gate was estimated to be about 2 x 106 cm/s. Moreover, it was analyzed that the parasitic channel charging delay occupied a substantial proportion of the total delay due to a large sheet resistance of the Ga2O3 channel and thus limited their high frequency device performance. These results suggest that both suppressing the short channel effect with a reduction in Lg to the sub 0.1 mm range and minimizing the access resistance are important to further improve RF device characteristics of Ga2O3 MOSFETs.
author_names: Takafumi Kamimura

Yoshiaki Nakata

Masataka Higashiwaki
title: Delay time analysis in radio frequency b Ga2O3 field effect transistors
year: 2020

abstract: The path to achieving integrated RF and power conversion circuitry using the b Ga2O3 material system is described with regard to the materials high Johnson's RF figure of merit. Recent results, including large signal data at VD 50 V, are provided, showing progress in achieving high voltage RF operation. Additionally, progress in achieving high gain devices through gate length scaling is also benchmarked by a record RF power device with a gate length of 0.5 mm achieving a 2.1 GHz mm f T L G product. These results are compared with state of the art RF devices, and the expectations for b Ga2O3 at this point in its maturity throughout this Letter with future milestones laid out to measure progress. The conclusion includes near and long term projections for b Ga2O3 devices for RF based on the results and projected milestones presented.
author_names: Neil A Moser

Kyle J Liddy

Ahmad E Islam

Nicholas C Miller

Kevin D Leedy

Thaddeus J Asel

Shin Mou

Andrew J Green

Kelson D Chabak
title: Toward high voltage radio frequency devices in b Ga2O3
year: 2020

abstract: We propose stability enhancement of a high frequency (1.2MHz) DC distribution network comprising numerous feedback controlled buck converters by replacing their conventional electro mechanical switches with \beta $polymorphic Gallium Oxide \beta \mathrm{Ga}_{2}\mathrm{O}_{3} power MOSFETs operated on soft switching. The performance anomaly in terms of output voltage oscillations and poor overall stability resulting from negative incremental impedances have been successfully addressed with the help of the Middlebrook Criterion. Having the highest Johnson's Figure of Merit (2844) among all studied Wide Band Gap (WBG) materials, \beta \mathrm{G}\mathrm{a}_{2}\mathrm{O}_{3} promises the best Power Frequency operation. In our simulations here, it leads to substantial performance improvement compared to the conventional system design in terms of output voltage oscillation and overall stability of the DCdistribution network Losses have been calculated and analyzed, with regard to the Minimum System Efficiency Degradation versus Maximum Stability Enhancement trade off. Further, we demonstrate the dominance of a solid state switch at the converter input, over a feedback loop at the back end, in securing a system with higher stability.
author_names: Sudipta Mukherjee

Dipankar Saha

Apurba Laha

Swaroop Ganguly
title: Stability Enhancement of High Frequency DC Distribution Network by Incorporating Wide Bandgap b Ga2O3 Power MOSFET as Switching Element
venue: 2020 IEEE Electric Power and Energy Conference (EPEC)
year: 2020

abstract: A high frequency diode is an essential component in electrical circuits providing the current rectification function for AC/DC converters, radio frequency detectors, and automotive inverters. Schottky barrier diodes based on wide bandgap semiconductors are promising for the high frequency applications owing to short reverse recovery time that minimizes the energy dissipation during the switching. In this study, we report dynamic characteristics of Schottky junctions composed of a layered oxide metal PdCoO2 and an n type b Ga2O3 substrate. Rectifying current voltage characteristics with reasonably small hysteresis were demonstrated up to a high frequency of 3 MHz in the PdCoO2/b Ga2O3 Schottky junctions. For the on state to off state switching with the current ramp rate of approximately 2 x 1010 A/scm2, the reverse recovery time was as short as 11 ns. The short reverse recovery time was constantly obtained in the operation temperature range of 25 350 degC, showing low loss switching properties of the PdCoO2/b Ga2O3 Schottky junctions. The Schottky barrier height of ~1.78 eV and the ideality factor of ~1.06 were maintained after the 108 times on off switching cycles. The fast switching with less energy dissipation and high durability of the PdCoO2/b Ga2O3 Schottky junctions would be suitable for application in high frequency power devices operating at high temperature.
author_names: Takayuki Harada

Atsushi Tsukazaki
title: Dynamic characteristics of PdCoO2/b Ga2O3 Schottky junctions
year: 2020

abstract: Abstract: During the last decade, silicon on insulator (SOI) metal oxide semiconductor field effect transistor (MOSFET) technology has demonstrated its high frequency potential, reaching cut off frequencies close to 500 GHz, and its suitability for commercial applications in harsh environments. For high speed and radio frequency (RF) applications, strained Si and high resistivity Si can be considered, respectively, to enhance carrier mobility and thus current and operation speed, and to minimize the RF substrate losses. Nowadays, substrate resistivity values higher than 5 kO.cm can easily be achieved and high resistivity silicon is widely seen as a promising substrate for radio frequency integrated circuits and mixed signal applications.
author_names: J P Raskin

Mostafa Emam
title: Silicon on insulator (SOI) metal oxide semiconductor field effect transistors (MOSFETs) for radio frequency (RF) and analogue applications
year: 2014

abstract: The superior electronic properties of ultra wide bandgap (UWBG) b gallium oxide (b Ga<inf>2</inf>O<inf>3</inf> gives promise to developing power and radio frequency (RF) devices with improved size, weight, and power (SWaP) and efficiency over current state of the art wide bandgap (WBG) devices based on SiC and GaN. However, self heating is viewed as a major challenge that the b Ga<inf>2</inf>O<inf>3</inf> device technology will encounter. b Ga<inf>2</inf>O<inf>3</inf> devices are expected to handle higher power densities than WBG counterparts. However, the thermal conductivity of b Ga<inf>2</inf>O<inf>3</inf> is only on the order of 10 20 W/m K, which is significantly lower than that for GaN or SiC. Therefore, large temperature gradients forming in b Ga<inf>2</inf>O<inf>3</inf> devices during operation can cause thermo mechanical reliability issues. In this work, a micro Raman metrology scheme was established to simultaneously measure the temperature rise and associated thermo elastic stress induced in b Ga<inf>2</inf>O<inf>3</inf> thin films. To decouple the effect of temperature and stress, the proposed scheme utilizes multiple peaks in the b Ga<inf>2</inf>O<inf>3</inf> Raman spectrum. A 1 mm thick halide vapor phase epitaxy (HVPE) b Ga<inf>2</inf>O<inf>3</inf> layer grown on a sapphire substrate and a 3D thermo mechanical multi physics model was utilized to establish the measurement technique. The developed method can be used to determine the stress and temperature in b Ga<inf>2</inf>O<inf>3</inf> epi layers consisting future UWBG electronic devices.
author_names: Bikramjit Chatterjee

Jacob H Leach

Sarit Dhar

Sukwon Choi
title: Temperature and Stress Metrology of Ultra Wide Bandgap b Ga2O3 Thin Films
venue: 2018 17th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)
year: 2018

abstract: Junctionless Metal Oxide Semiconductor Field Effect Transistor (JL MOSFET) is one of the promising candidate to replace the junction based MOSFET for upcoming technology nodes. Semiconductor industries are continuously urging for large ON current with the low OFF current and low specific on resistance. However, high ON current is achieved in Conventional (Conv. JL DG MOSFET by using high doping concentration at the cost of high OFF current which leads depletion mode operation. Moreover, low doping, narrow channel thickness and high work function gate materials are using to operate Conv. JL DG MOSFET in enhancement mode (V th 0 V for N JL DG MOSFET, V th 0 V for P JL DG MOSFET) but ON current is reduced in all above mentioned solutions. To overcome the above mentioned problems, a new architecture is developed called Recessed JL DG MOSFET. In Recessed JL DG MOSFET silicon region is recessed under the gate region and some gate portion is extended towards source and drain region. Recessed JL DG MOSFET shows the same ON current as achieved in Conv. JL DG MOSFET with very low OFF current (leakage current) by considering high doping concentration. Surface potential, electron density, energy band distribution, drain current have been investigated to proof the enhancement mode operation of Recessed JL DG MOSFET. Figure of Merits (FOMs) for RF performance such as Trans conductance, capacitance and intrinsic power gain (S 21 Trans conductance frequency product (TFP) Gain frequency product (GFP) and Gain trans conductance frequency product (GTFP) have also investigated of Recessed JL DG MOSFET.
title: Investigation of Recessed Junctionless Double Gate MOSFET for Radio Frequency Applications
venue: Silicon
year: 2020

abstract: This paper presents a new extraction method for source and drain (S/D) series resistances of silicon nanowire (SNW) metal oxide semiconductor field effect transistors (MOSFETs) based on small signal radio frequency (RF) analysis. The proposed method can be applied to the extraction of S/D series resistances for SNW MOSFETs with finite off state channel resistance as well as gate bias dependent on state resistive components realized by 3 dimensional (3 D) device simulation. The series resistances as a function of frequency and gate voltage are presented and compared with the results obtained by an existing method with infinite off state channel resistance model. The accuracy of the newly proposed parameter extraction method has been successfully verified by Z22 and Y parameters up to 100 GHz operation frequency.
author_names: Jae Hwa Hwa

Young Jun Yoon

Hwan Gi Lee

Gwan Min Yoo

Eou Sik Cho

Seongjae Cho

Jung-Hee Lee

In Man Kang
title: A reliable extraction method for source and drain series resistances in silicon nanowire metal oxide semiconductor field effect transistors (MOSFETs) based on radio frequency analysis.
venue: Journal of nanoscience and nanotechnology
year: 2014