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Huang S.,Hong Kong University of Science and Technology | Yang S.,Hong Kong University of Science and Technology | Roberts J.,Nitronex Corp | Chen K.J.,Hong Kong University of Science and Technology
Japanese Journal of Applied Physics | Year: 2011

The threshold voltage (Vth) instability in GaN-based metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) with 15-nm atomic-layer-deposited (ALD) Al2O3 as gate dielectrics is systematically investigated by dc current-voltage (I-V), high-frequency capacitance- voltage (C-V) (HFCV), and quasi-static C-V (QSCV) characterizations. Both Al2O3/GaN/AlGaN/GaN MIS diode and GaN/AlGaN/GaN Schottky diode only exhibit tiny threshold-voltage hysteresis (δVth) (> 10 mV) in double-mode (up and down sweep) HFCV characteristics as the maximum forward bias (VF,max) during the sweep is set to 0 V, while an apparent δVth (as large as 0.9 V) emerges as VF,max is increased to +5 V for the MIS diode. The stability of Vth in the corresponding MIS-HEMTs is thus studied by increasing the maximum VGS (VGS,max) in the measurement of transfer characteristics. Significant positive Vth shift occurred once the VGS,max exceeds +1 V, while such Vth-instability is still absent in Schottky-gate AlGaN/GaN HEMTs. It is suggested that the acceptor-like deep states at Al2O3/GaN interface account for the Vth-instability in Al2O3/GaN/AlGaN/GaN MIS-HEMTs. As the filling and emission processes of these interface states are slow, they are successfully captured by low-frequency QSCV techniques. © 2011 The Japan Society of Applied Physics.


Huang S.,Hong Kong University of Science and Technology | Yang S.,Hong Kong University of Science and Technology | Roberts J.,Nitronex Corp | Chen K.J.,Hong Kong University of Science and Technology
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2012

The threshold-voltage (V th) instability in AlGaN/GaN MIS-HEMTs with ALD-Al 2O 3 (15 nm) as gate dielectrics is systematically investigated by dc current-voltage (I-V), high-frequency capacitance-voltage (C-V) (HFCV), and quasi-static C-V (QSCV) characterizations. For Al 2O 3/GaN/AlGaN/GaN MIS diodes, tiny V th hysteresis (ΔV th) appears in double-mode (up and down sweep) HFCV measurements if the maximum forward bias (V F,max) is only set to 0 V, while an apparent clockwise ΔV th (as large as 0.9 V) emerges as V F,max is increased to +5 V. The stability of V th in the corresponding MIS-HEMTs is thus studied by increasing the maximum V GS (V GS,max) in the measurement of double-mode transfer characteristics. Significant clockwise ΔV th also occurred once the V GS,max exceeds +1.1 V, and it increased to ∼1 V at V GS,max= +3 V. Such V th-instability is absent in AlGaN/GaN HEMTs. It is suggested that the acceptor-like deep states at Al 2O 3/GaN interface account for the V th-instability in Al 2O 3/GaN/AlGaN/GaN MIS-HEMTs, and their filling and emission processes are successfully captured by QSCV measurements. The interface state density detected is about 4.6×10 12 cm -2 using 1 Hz QSCV. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Marti D.,ETH Zurich | Tirelli S.,ETH Zurich | Alt A.R.,ETH Zurich | Roberts J.,Nitronex Corp | Bolognesi C.R.,ETH Zurich
IEEE Electron Device Letters | Year: 2012

We report a new generation of high-performance AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on high-resistivity Si (111) substrates. We map out small-and large-signal device performances against technological parameters such as the gate length and the source-drain contact separation. We report the first large-signal performance for a GaN-on-Si technology offering an output power of 2 W/mm and an associated peak power-added efficiency of 13.8% (peak of 18.5%) at 40 GHz without any field plate. The technology offers measured transconductances of up to 540 mS/mm and cutoff frequencies as high as $f-{\rm T}/f-{\rm MAX} = \hbox{152/149}\ \hbox{GHz}$ at a given bias point. These are the highest cutoff frequencies to date for fully passivated AlGaN/GaN HEMTs on silicon substrates. The results confirm GaN-on-Si technology as a promising contender for low-cost millimeter-wave power electronic applications. © 2012 IEEE.


Lu B.,Massachusetts Institute of Technology | Piner E.L.,Nitronex Corp | Palacios T.,Massachusetts Institute of Technology
IEEE Electron Device Letters | Year: 2010

In this letter, we demonstrate 27% improvement in the buffer breakdown voltage of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on Si substrate by using a new Schottky-drain contact technology. Schottky-drain AlGaN/GaN HEMTs with a total 2-μm-thick GaN buffer showed a three-terminal breakdown voltage of more than 700 V, while conventional AlGaN/GaN HEMTs of the same geometry showed a maximum breakdown voltage below 600 V. The improvement of the breakdown voltage has been associated with the planar contact morphology and lack of metal spikes in the Schottky-drain metallization. © 2010 IEEE.


Gokhale V.J.,University of Michigan | Roberts J.,Nitronex Corp | Rais-Zadeh M.,University of Michigan
2011 16th International Solid-State Sensors, Actuators and Microsystems Conference, TRANSDUCERS'11 | Year: 2011

In this paper, measurements and characterization results of several micromechanical bulk-mode resonators and filters fabricated from single crystalline gallium nitride are presented. A 167.6 MHz length-extensional mode resonator is demonstrated that exhibits an unloaded quality factor of 1370 and motional impedance of 485 ω at atmospheric pressure and 300 K. The f×Q values of the resonators presented in this work measured under ambient conditions are significantly higher than prior work and prove that GaN is a suitable material as a micromechanical resonating element for high-power applications. The relevant material properties of GaN are also characterized. © 2011 IEEE.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.92K | Year: 2012

The future capabilities of sensors and instrumentation deployed in space will continue to increase, resulting in increasing amounts of collected data. To reach these higher speed data rates, increases to the overall system gain of the communication link will be required. A deterministic method to increase system gain of a RF communication link is to provide higher transmitted RF power. However, with this higher RF output power also comes the challenge of maximizing power efficiency and reducing the size weight and power (SWAP) of the power amplifier (PA) for long-range space missions.The innovation will be to develop a Solid-State Power Amplifier (SSPA) that produces 50 W of linear RF at X-Band (8.4 GHz) with high DC-to-RF-efficiency (>60%) and low mass. The significance will be the utilization of wide band-gap RF semiconductors to efficiently create high RF power that is robust to the high radiation environments of space. A wide band-gap compound semiconductor material such as Gallium Nitride (GaN) will provide this required innovation.GaN-based Field Effect Transistors (FETs) have the potential to operate at power densities of up to 10 times that of conventional RF semiconductor technologies, which will enable compact PAs with higher RF output power to be implemented. The proposed GaN PA design is estimated to be>50% smaller in both size and weight compared to other solid state solutions and almost 20% lower in power consumption for typical designs used in long-range space RF Telecommunications.In summary, Applying novel GaN semiconductor materials in innovative PA designs are required for long-range space RF communication systems to fully reach their performance potential and to reduce their SWAP.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 99.91K | Year: 2011

Nitronex Corporation has identified unique innovations in Gallium Nitride (GaN) high electron mobility transistors (HEMT) for realizing advancements in X and Ka-Band low noise amplifiers (LNAs). These advancements are based on existing GaN on silicon (Si), radio frequency (RF) power amplifier (PA) device techniques and when applied to LNAs, improve Satellite Communication (SATCOM) receiver systems in the presence of wideband high powered RF signals. It is well established that GaN based semiconductor structures, specifically AlGaN/GaN heterostructures, provide advantages over GaAs, SiC, Si, & SiGe in the domain of high power operation. GaN-based materials have wide bandgap and high breakdown fields, which allow the device to operate at a voltage>2.5 times the maximum operating voltage of a GaAs device. The reduction in signal distortion due to non-linearity of a LNA or a low noise block downconverter (LNB), while maintaining low noise figure is of particular significance to SATCOM systems The proposed GaN on Si technology will produce cost effective LNA and LNB building blocks that are highly-reliable, extremely linear and very robust to signal overload in X and Ka-Band SATCOM applications. BENEFIT: The proposed GaN on Si technology will produce cost effective LNA and LNB building blocks with high performance for use in military and commercial SATCOM applications at X or Ka-Band.


Semiconductor structures including one, or more, III-nitride material regions (e.g., gallium nitride material region) and methods associated with such structures are provided. The III-nitride material region(s) advantageously have a low dislocation density and, in particular, a low screw dislocation density. In some embodiments, the presence of screw dislocations in the III-nitride material region(s) may be essentially eliminated. The presence of a strain-absorbing layer underlying the III-nitride material region(s) and/or processing conditions can contribute to achieving the low screw dislocation densities. In some embodiments, the III-nitride material region(s) having low dislocation densities include a gallium nitride material region which functions as the active region of the device. The low screw dislocation densities of the active device region (e.g., gallium nitride material region) can lead to improved properties (e.g., electrical and optical) by increasing electron transport, limiting non-radiative recombination, and increasing compositional/growth uniformity, amongst other effects.


LOWELL, Mass.--(BUSINESS WIRE)--M/A-COM Technology Solutions Holdings, Inc. (NASDAQ: MTSI) (“MACOM”), a leading supplier of high-performance analog RF, microwave, millimeterwave and photonic semiconductor products, today announced a revision to its financial results for its fiscal second quarter ended April 3, 2015, as originally reported on April 28, 2015. In May 2015, subsequent to MACOM’s April 28, 2015 fiscal second quarter 2015 earnings press release but prior to the filing of its Quarterly Report on Form 10-Q for the fiscal second quarter ended April 3, 2015, MACOM received notice that a private company in which it held a minority equity investment was sold to a third party and the proceeds MACOM would receive at closing would be less than the carrying value previously reported on MACOM’s consolidated financial statements in the April 28, 2015 earnings release. As required under U.S. generally accepted accounting principles (GAAP), MACOM wrote-down the investment to the estimated the net proceeds that MACOM will receive from the sale, and recorded a charge of $3.5 million to other income (expense), resulting in an increase of its net loss per diluted share of $0.05, or $0.15 and $0.28 net loss per diluted share for the three and six months ended April 3, 2015, respectively. This non-cash, non-operating charge did not affect MACOM’s previously reported non-GAAP earnings per share of $0.41 in the fiscal second quarter of 2015. A reconciliation between revised GAAP and non-GAAP financial data is included in the supplemental financial data attached to this press release. The revised financial statements reflecting the impairment of the minority equity investment are also attached to this press release. M/A-COM Technology Solutions Holdings, Inc. (www.macom.com) is a leading supplier of high-performance analog RF, microwave, millimeterwave and photonic semiconductor products that enable next-generation internet and modern battlefield applications. Recognized for its broad catalog portfolio of technologies and products, MACOM serves diverse markets, including high speed optical, satellite, radar, wired and wireless networks, automotive, industrial, medical, and mobile devices. A pillar of the semiconductor industry, we thrive on more than 60 years of solving our customers' most complex problems, serving as a true partner for applications ranging from RF to Light. Headquartered in Lowell, Massachusetts, MACOM is certified to the ISO9001 international quality standard and ISO14001 environmental management standard. MACOM has design centers and sales offices throughout North America, Europe, Asia and Australia. MACOM, M/A-COM, M/A-COM Technology Solutions, M/A-COM Tech, Partners in RF & Microwave, The First Name in Microwave and related logos are trademarks of MACOM. All other trademarks are the property of their respective owners. This press release contains forward-looking statements based on MACOM management's beliefs and assumptions and on information currently available to our management. Forward-looking statements include, among others, information concerning our stated business outlook and future results of operations, our statements regarding having the right strategy, addressing the right secular growth drivers, with the correct technology, intellectual property and leadership team to assure long term success, and any statements regarding future trends, business strategies, competitive position, industry conditions, acquisitions and market opportunities. Forward-looking statements include all statements that are not historical facts and generally may be identified by terms such as "anticipates," "believes," "could," "estimates," "expects," "intends," "may," "plans," "potential," "predicts," "projects," "seeks," "should," "will," "would" or similar expressions and the negatives of those terms. Forward-looking statements contained in this press release reflect MACOM's current views about future events and are subject to risks, uncertainties, assumptions and changes in circumstances that may cause those events or our actual activities or results to differ materially from those expressed in any forward-looking statement. Although MACOM believes that the expectations reflected in the forward-looking statements are reasonable, it cannot and does not guarantee future events, results, actions, levels of activity, performance or achievements. Readers are cautioned not to place undue reliance on these forward-looking statements. A number of important factors could cause actual results to differ materially from those indicated by the forward-looking statements, including greater than expected dilutive effect on earnings of our equity issuances, outstanding indebtedness and related interest expense and other costs, lower than expected demand in any or all of our four primary end markets or from any of our large OEM customers based on seasonal effects, macro-economic weakness or otherwise, our failure to realize the expected economies of scale, lowered production cost and other anticipated benefits of our previously announced GaN intellectual property licensing program or InP laser production capacity expansion program, the potential for defense spending cuts, program delays, cancellations or sequestration, failures or delays by any customer in winning business or to make purchases from us in support of such business, lack of adoption or delayed adoption by customers and industries we serve of GaN, InP lasers or other solutions offered by us, failures or delays in porting and qualifying GaN or InP process technology to our Lowell, MA fabrication facility or third party facilities, lower than expected utilization and absorption in our manufacturing facilities, lack of success or slower than expected success in our new product development efforts, loss of business due to competitive factors, product or technology obsolescence, customer program shifts or otherwise, lower than anticipated or slower than expected customer acceptance of our new product introductions, the potential for a shift in the mix of products sold in any period toward lower-margin products or a shift in the geographical mix of our revenues, the potential for increased pricing pressure based on competitive factors, technology shifts or otherwise, the impact of any executed or abandoned acquisition, divestiture, joint venture, financing or restructuring activity, the impact of supply shortages or other disruptions in our internal or outsourced supply chain, the impact of changes in export, environmental or other laws applicable to us, the relative success of our cost-savings initiatives, the potential for inventory obsolescence and related write-offs, the expense, business disruption or other impact of any current or future investigations, administrative actions, litigation or enforcement proceedings we may be involved in, the potential loss of access to any in-licensed intellectual property or inability to license technology we may require on reasonable terms, and the impact of any claims of intellectual property infringement or misappropriation, which could require us to pay substantial damages for infringement, expend significant resources in prosecuting or defending such matters or developing non-infringing technology, incur material liability for royalty or license payments, or prevent us from selling certain of our products, as well as those factors described in "Risk Factors" in MACOM's filings with the Securities and Exchange Commission (SEC), including its Quarterly Report on Form 10-Q for the second fiscal quarter ended April 3, 2015 as filed with the SEC on May 13, 2015. MACOM undertakes no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise. In addition to GAAP reporting, MACOM provides investors with non-GAAP financial information, including revenue, gross margin, operating margin, operating income, net income, earnings per share, EBITDA and other data calculated on a non-GAAP basis. This non-GAAP information excludes the operations of Nitronex prior to the date of acquisition, discontinued operations, the impact of fair value accounting in merger and acquisitions (M&A) of businesses, M&A costs, including acquisition and related integration costs, certain cost savings from synergies expected from M&A activities, income and expenses from transition services related to M&A activities, expected amortization of acquisition-related intangibles, share-based and other non-cash compensation expense, certain cash compensation, restructuring charges, litigation settlement and costs, changes in the carrying values of assets and liabilities measured at fair value, contingent consideration, amortization of debt discounts and issuance costs, other non-cash expenses, earn-out costs, exited leased facility costs and certain income tax items. Management does not believe that the excluded items are reflective of MACOM's underlying performance. The exclusion of these and other similar items from MACOM's non-GAAP presentation should not be interpreted as implying that these items are non-recurring, infrequent or unusual. These and other similar items are also excluded from EBITDA, which is non-GAAP earnings before interest, income taxes, depreciation and amortization. MACOM believes this non-GAAP financial information provides additional insight into MACOM's on-going performance and has, therefore, chosen to provide this information to investors for a consistent basis of comparison and to help them evaluate the results of MACOM's on-going operations and enable more meaningful period to period comparisons. These non-GAAP measures are provided in addition to, and not as a substitute for, or superior to, measures of financial performance prepared in accordance with GAAP. A reconciliation between GAAP and non-GAAP financial data is included in the supplemental financial data attached to this press release.

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