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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.

Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase II | Award Amount: 868.98K | Year: 2008

AlGaN/GaN FETs on Si will be developed and optimized for operation at high frequency (X-band and above). The high frequency performance will be improved by modifications to the existing commercialized sub-4GHz GaN FET platform technology that’s currently available at Nitronex. The modifications will be made in the epitaxial structure, device layout and gate length for maximum X-band radar performance. In parallel, research will be conducted on surface issues that influence device performance and reliability. Novel MgCaO dielectric will be investigated for suitability for high performance GaN HEMTs at all frequencies. Physical modeling using Monte Carlo simulation will also be performed to gain insight into HEMT performance and reliability. Once the basic process modules are developed, a fabrication run will be undertaken to produce high frequency discrete devices and MMICs that are suitable for use with the X-band radar PA. The GaN device technology that will be developed in this program will satisfy the needs of MDA BMDS systems at X-band and also enable new commercial applications for GaN FETs in the area of weather radar, commercial avionics, satellite communications and high frequency WiMAX wireless communications.

Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase II | Award Amount: 750.00K | Year: 2008

GaN HEMTs have the ability to delivery very high power levels when operated at at high voltages (48V). Therefore, they are ideally suited for high power amplifiers such as the E2C HPA used in the Advanced Hawkeye aircraft. The current version of the E2C HPA utilizes silicon technology. We propose to develop a reliable 300W GaN packaged device that can be used to develop a significantly lighter and smaller HPA. Specifically, we will be replacing 21 silicon devices with only 5 GaN devices, which is estimated to reduce weight by a factor of 2 with a new system design. Further, we will develop such a device on the reliable GaN FET on Si platform technology that is fully qualified for military and commercial applications. The MTTF of our GaN FET technology is >10 million hours at a Tj of 150 degress celsius.

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.

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