D. Buttari

Northrop Grumman (United States)

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Umesh K. Mishra

University of California, Santa Barbara

S. Keller

University of California, Santa Barbara

Alessandro Chini

University of Modena and Reggio Emilia

S. Heikman

Cree (China)

R. Coffie

Northrop Grumman (United States)

L. Shen

University of Oxford

Steven P. DenBaars

University of California, Santa Barbara

A. Chakraborty

University of Missouri

E. Zanoni

University of Padua

Gaudenzio Meneghesso

University of Padua

Cooperative Institutions

University of California, Santa Barbara

Northrop Grumman (United States)

University of Padua

Northrop Grumman (United Kingdom)

Redondo Optics (United States)

Northrop Grumman (Germany)

Transphorm (United States)

TRW Automotive (United States)

University of Michigan–Ann Arbor

Vanderbilt University

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P-GaN/AlGaN/GaN high electron mobility transistors

R. Coffie S. Heikman D. Buttari Sarah L. Keller Alessandro Chini

Despite the considerable improvement in GaN-technology and material quality, RF-dispersion is still one of the main issues hampering device progress. RF-dispersion affects device output power and device power added efficiency (PAE) due to a reduction in saturation current and an increase in knee voltage at high frequencies and high biases. Surface passivation, using silicon nitride, has been found to mitigate RF-dispersion and microwave power degradation (B.M. Green et al, IEEE Electron Dev. Lett., vol. 21, pp. 268-270, 2000; S.C. Binari et al, IEEE Trans Electron. Dev., vol. 48, pp. 465-471, 2001; R. Vetury et al, ibid., vol. 48, pp. 560-566, 2001). This paper discusses a novel AlGaN/GaN high electron mobility transistor (HEMT) device structure which has been developed to reduce RF-dispersion prior to silicon nitride passivation. The device structure uses a p-doped GaN cap layer to screen surface potential changes (regardless of origin) from affecting the gate-drain access region resistance, reducing the amount of RF-dispersion in the device. The epilayers of AlGaN/GaN devices were grown by metal organic chemical vapor deposition (MOCVD) on a c-plane sapphire substrate. Sheet electron concentration and electron Hall mobility of the as-grown wafer were /spl sim/1.35/spl times/10/sup 13/ cm/sup 2/ and 1,475 cm/sup 2//V-s at room temperature.

Passivation

Electron Mobility

10.1109/drc.2002.1029489

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Citations (3)

Use of double-channel heterostructures to improve the access resistance and linearity in GaN-based HEMTs

IEEE Transactions on Electron Devices (2006)

Tomás Palacios Alessandro Chini D. Buttari S. Heikman A. Chakraborty

Double-channel structures have been used in AlGaN/GaN high electron mobility transistors to reduce the access resistance. Carrier densities as high as 2.9/spl times/10/sup 13/ cm/sup -2/ and mobilities in the 1300 cm/sup 2//V/spl middot/s range have been obtained in the access region. Also, the correct design of the potential barrier between the different channels allowed tailoring the differential access resistance to enhance the linearity of the transistors. This increase in linearity has been measured as a flatter profile of the transconductance and cutoff frequency versus current and as an improvement of more than 2 dB in large-signal two-tone linearity measurements.

Linearity

Transconductance

Cutoff frequency

10.1109/ted.2005.863767

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Citations (94)

High-Power Polarization-Engineered GaN/AlGaN/GaN HEMTs Without Surface Passivation

IEEE Electron Device Letters (2004)

L. Shen R. Coffie D. Buttari S. Heikman A. Chakraborty

In this paper, a high-power GaN/AlGaN/GaN high electron mobility transistor (HEMT) has been demonstrated. A thick cap layer has been used to screen surface states and reduce dispersion. A deep gate recess was used to achieve the desired transconductance. A thin SiO/sub 2/ layer was deposited on the drain side of the gate recess in order to reduce gate leakage current and improve breakdown voltage. No surface passivation layer was used. A breakdown voltage of 90 V was achieved. A record output power density of 12 W/mm with an associated power-added efficiency (PAE) of 40.5% was measured at 10 GHz. These results demonstrate the potential of the technique as a controllable and repeatable solution to decrease dispersion and produce power from GaN-based HEMTs without surface passivation.

Passivation

Transconductance

Wide-bandgap semiconductor

Power density

10.1109/led.2003.821673

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Citations (111)

Proton-Induced Damage in Gallium Nitride-Based

Aditya P. Karmarkar B. D. White D. Buttari Daniel M. Fleetwood Ronald D. Schrimpf

Proton irradiation decreases the doping concentra- tion and increases the ideality factor and series resistance, but has very little effect on the Schottky barrier height in n-Gallium nitride Schottky diodes. 1.0-MeV protons cause greater degrada- tion than 1.8-MeV protons because of their higher nonionizing energy loss. The displacement damage recovers during annealing. Comparison between Schottky diodes and high electron-mobility transistors suggests that the degradation in both types of devices is predominantly due to carrier removal and mobility degradation caused by radiation-induced defect centers in the crystal lattice, with interface disorder playing a relatively insignificant part in overall device degradation.

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Demonstration of a GaN‐spacer high electron mobility transistor with low alloy scattering

physica status solidi (a) (2005)

Tomás Palacios L. Shen S. Keller A. Chakraborty S. Heikman

Abstract A new kind of high electron mobility transistor (HEMT) based on a GaN‐spacer is reported. To confine the two‐dimensional electron gas in this AlGaN‐free HEMT, a GaN/ultrathin AlN/GaN pseudo‐hetero‐junction has been used. The effective conduction band discontinuity is given by the AlN polarization‐induced electric field. This new transistor shows a superior general performance than the standard HEMT due to a decrease in the alloy and real space transfer scattering, as well as lower ohmic contact resistance. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ohmic contact

Electron Mobility

Wide-bandgap semiconductor

10.1002/pssa.200461563

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Citations (9)

On-state breakdown measurements in GaAs MESFETs and InP-based HEMTs

E. Zanoni Gaudenzio Meneghesso Andrea Bortoletto M. Maretto G. Massari

MESFET

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Improvement of DC, low frequency and reliability properties of InAlAs/InGaAs InP-based HEMTs by means of an InP etch stop layer

Gaudenzio Meneghesso D. Buttari E. Perin C. Canali E. Zanoni

In this paper we report on the elimination of the kink effect and of the hot-electron degradation in InP-based HEMTs which results from the insertion of an InP etch stop layer on top of the InAlAs donor layer. We attribute this improvement to the passivation, by means of InP, of deep levels on the surface of the InAlAs, as demonstrated by transconductance frequency dispersion measurements.

Passivation

Transconductance

Degradation

Indium gallium arsenide

Indium phosphide

10.1109/iedm.1998.746341

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Citations (37)

Progressive Schottky junction reaction induced degradation in Pt-sunken gate InP HEMT MMICs for high reliability applications

Y.C. Chou D. Leung M. Biedenbender D. Buttari D. Eng

Reliability performance of 0.1-μm Pt-sunken gate InP HEMT MMICs on 4-inch InP substrates was evaluated under elevated temperature life testing. The primary degradation mechanism was observed to be the progressive Schottky junction reaction with the Schottky barrier InAlAs and the InGaAs channel. Despite the progressive Schottky junction reaction with the InAlAs and InGaAs materials, the lifetest at T _ambient of 280°C projects the median-time-to-failure exceeding 1×10 ⁶ hours at T _channel of 125°C. This result indicates that the promising initial reliability performance was achieved on Pt-sunken gate InP HEMT MMICs on 4-inch InP substrates.

Degradation

10.1109/irps.2010.5488728

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Citations (1)

SELECTIVE DRY ETCHING OF GaN OVER AlGaN IN BCL₃/SF₆ MIXTURES

International Journal of High Speed Electronics and Systems (2004)

D. Buttari Alessandro Chini A. Chakraborty L. McCarthy Huili Grace Xing

Inductively coupled plasma (ICP) etching of GaN with high selectivity over Al .22 Ga .78 N in BCl 3 / SF 6 mixtures has been studied. Selectivity and surface morphology were investigated over a wide range of pressures (3.75–37.5mTorr), RF powers (30–120 W), ICP powers (100–400 W), and SF 6 / BCl 3 ratios (0.1–0.7). Higher pressures, lower dc biases, and higher SF 6 / BCl 3 ratios increased the GaN to AlGaN selectivity. Selectivities up to 25 were measured by laser interferometry. A root mean square (rms) surface roughness of 0.67 nm was measured by atomic force microscopy (AFM) after removal of 0.5 μm from a GaN template (process selectivity: 15, as-grown rms surface roughness: 0.56 nm). A degradation in surface morphology, with the gradual formation of pits, was observed for selectivities above 10.

Font

Root mean square

10.1142/s012915640400279x

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Citations (37)

AlGaN/AlN/GaN High Electron Mobility Transistors with Improved Carrier Transport

Conference on Optoelectronic and Microelectronic Materials and Devices (2006)

Giacinta Parish Gilberto A. Umana‐Membreno S.M. Jolley D. Buttari S. Keller

Geo-magneto-resistance measurements have been made on AlGaN/GaN HEMT structures both with and without an AlN interlayer. The results show significantly higher carrier mobility at low temperatures for devices with the interlayer. Furthermore, the drop in mobility with increasing 2DEG density, commonly exhibited by AlGaN/GaN HEMTs, is dramatically reduced by introduction of the interlayer. These results provide insight into the role of alloy and interface roughness scattering on 2DEG properties

Electron Mobility

Wide-bandgap semiconductor

10.1109/commad.2004.1577484

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Citations (11)