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AlGaN High Electron Mobility Transistor for Power Switches and High Temperature Logic

Klein, Brianna A.; Armstrong, Andrew A.; Allerman, A.A.; Nordquist, Christopher N.; Neely, Jason C.; Reza, Shahed R.; Douglas, Erica A.; Van Heukelom, Michael V.; Rice, Anthony R.; Patel, Victor J.; Matins, Benjamin M.; Fortune, Torben R.; Rosprim, Mary R.; Caravello, Lisa N.; DeBerry, Rebecca N.; Pipkin, Jennifer R.; Abate, Vincent M.; Kaplar, Robert K.

Abstract not provided.

Nanoantenna-Enhanced Resonant Detectors for Improved Infrared Detector Performance

Goldflam, Michael G.; Anderson, Evan M.; Fortune, Torben R.; Klem, John F.; Hawkins, Samuel D.; Davids, Paul D.; Campione, Salvatore; Pung, Aaron J.; Webster, Preston T.; Weiner, Phillip H.; Finnegan, Patrick S.; Wendt, Joel R.; Wood, Michael G.; Haines, Chris H.; Coon, Wesley T.; Olesberg, Jonathon T.; Shaner, Eric A.; Kadlec, Clark N.; Beechem, Thomas E.; Sinclair, Michael B.; Tauke-Pedretti, Anna; Kim, Jin K.; Peters, D.W.

Abstract not provided.

Monolithically fabricated tunable long-wave infrared detectors based on dynamic graphene metasurfaces

Applied Physics Letters

Goldflam, Michael G.; Ruiz, Isaac R.; Howell, S.W.; Tauke-Pedretti, Anna; Anderson, Evan M.; Wendt, J.R.; Finnegan, P.; Hawkins, Samuel D.; Coon, W.; Fortune, Torben R.; Shaner, Eric A.; Kadlec, Clark N.; Olesberg, Jonathon T.; Klem, John F.; Webster, Preston T.; Sinclair, Michael B.; Kim, Jin K.; Peters, D.W.; Beechem, Thomas E.

Here, the design, fabrication, and characterization of an actively tunable long-wave infrared detector, made possible through direct integration of a graphene-enabled metasurface with a conventional type-II superlattice infrared detector, are reported. This structure allows for post-fabrication tuning of the detector spectral response through voltage-induced modification of the carrier density within graphene and, therefore, its plasmonic response. These changes modify the transmittance through the metasurface, which is fabricated monolithically atop the detector, allowing for spectral control of light reaching the detector. Importantly, this structure provides a fabrication-controlled alignment of the metasurface filter to the detector pixel and is entirely solid-state. Using single pixel devices, relative changes in the spectral response exceeding 8% have been realized. These proof-of-concept devices present a path toward solid-state hyperspectral imaging with independent pixel-to-pixel spectral control through a voltage-actuated dynamic response.

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Stability in Fluorine-Treated Al-Rich High Electron Mobility Transistors with 85% Al-Barrier Composition

IEEE International Reliability Physics Symposium Proceedings

Baca, A.G.; Klein, B.A.; Armstrong, Andrew A.; Allerman, A.A.; Douglas, Erica A.; Fortune, Torben R.; Kaplar, Robert K.

Combined with recess etching, Al-rich III-N high electron mobility transistors (HEMTs) can be treated with a reactive ion etch plasma to implant F- ions into the HEMT's near surface region for a positive threshold voltage $(V-{TH})$ shift to achieve enhancement-mode (e-mode) operation. These HEMTs, along with depletion-mode (d-mode) controls that lack fluorine treatment, were evaluated for F- ion stability using step-stress and fixed-bias stress experiments. Step-stress experiments identified parametric shifts as a function of the drain-voltage $(V-{DS})$ stress prior to catastrophic failure that occurred at ${\it V-{DS}}$ ranging between 70-75 V. Fixed bias stressing at $V-{DS}=50\mathrm{V}$ was conducted at $190\ ^{\circ}\mathrm{C}$ Both e- and d- mode HEMTs exhibited a negative $V-{TH}$ shift of $0.6-1.0 \mathrm{V}$ during early time stressing at 190°C, with minor on-resistance effects, but both HEMT types were thereafter stable up to 4 hours. The early time changes are common to both e-mode and d-mode HEMTs and the F-induced ${\it V-{TH}}$ delta between e- and d-mode HEMTs remains intact within the bias-temperature stressing conditions of this work.

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Enhancement-mode Al0.85Ga0.15N/Al0.7Ga0.3N high electron mobility transistor with fluorine treatment

Applied Physics Letters

Klein, Brianna A.; Douglas, Erica A.; Armstrong, Andrew A.; Allerman, A.A.; Abate, Vincent M.; Fortune, Torben R.; Baca, A.G.

Enhancement-mode Al0.7Ga0.3N-channel high electron mobility transistors (HEMTs) were achieved through a combination of recessed etching and fluorine ion deposition to shift the threshold voltage (VTH) relative to depletion-mode devices by +5.6 V to VTH = +0.5 V. Accounting for the threshold voltage shift (ΔVTH), current densities of approximately 30 to 35 mA/mm and transconductance values of 13 mS/mm were achieved for both the control and enhancement mode devices at gate biases of 1 V and 6.6 V, respectively. Little hysteresis was observed for all devices, with voltage offsets of 20 mV at drain currents of 1.0 × 10-3mA/mm. Enhancement-mode devices exhibited slightly higher turn-on voltages (+0.38 V) for forward bias gate currents. Piecewise evaluation of a threshold voltage model indicated a ΔVTH of +3.3 V due to a gate recess etching of 12 nm and an additional +2.3 V shift due to fluorine ions near the AlGaN surface.

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Enhancement-mode AlGaN channel high electron mobility transistor enabled by p-AlGaN gate

Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics

Douglas, Erica A.; Klein, Brianna A.; Allerman, A.A.; Baca, A.G.; Fortune, Torben R.; Armstrong, Andrew A.

This work exhibits the ability to shift the threshold voltage of an Al0.45Ga0.55N/Al0.3Ga0.7N high electron mobility transistor through the implementation of a 100 nm thick p-Al0.3Ga0.7N gate. A maximum threshold voltage of +0.3 V was achieved with a 3 μm gate length. In addition to achieving enhancement-mode operation, this work also shows the capability to obtain high saturated drain current (>50 mA/mm), no gate hysteresis, high ION,MAX/IOFF,MIN ratio of >109, and exceptionally low gate leakage current of 10-6 mA/mm even under high forward bias of Vgs = 8 V.

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Al0.85Ga0.15N/Al0.70Ga0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

ECS Journal of Solid State Science and Technology

Baca, A.G.; Klein, Brianna A.; Allerman, A.A.; Armstrong, Andrew A.; Douglas, Erica A.; Stephenson, Chad A.; Fortune, Torben R.; Kaplar, Robert K.

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that are promising candidates for RF and power applications. Long-channel AlxGa1-xN HEMTs with x = 0.7 in the channel have been built and evaluated across the -50°C to +200°C temperature range. These devices achieved room temperature drain current as high as 46 mA/mm and were absent of gate leakage until the gate diode forward bias turn-on at ~2.8 V, with a modest -2.2 V threshold voltage. A very large Ion/Ioff current ratio, of 8 × 109 was demonstrated. A near ideal subthreshold slope that is just 35% higher than the theoretical limit across the temperature range was characterized. The ohmic contact characteristics were rectifying from -50°C to +50°C and became nearly linear at temperatures above 100°C. An activation energy of 0.55 eV dictates the temperature dependence of off-state leakage.

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Integrating Resonant Structures with IR Detectors

Goldflam, Michael G.; Goldflam, Michael G.; Anderson, Evan M.; Anderson, Evan M.; Campione, Salvatore; Campione, Salvatore; Coon, Wesley T.; Coon, Wesley T.; Davids, Paul D.; Davids, Paul D.; Fortune, Torben R.; Fortune, Torben R.; Hawkins, Samuel D.; Hawkins, Samuel D.; Kadlec, Clark N.; Kadlec, Clark N.; Kadlec, Emil A.; Kadlec, Emil A.; Kim, Jin K.; Kim, Jin K.; Klem, John F.; Klem, John F.; Shaner, Eric A.; Shaner, Eric A.; Sinclair, Michael B.; Sinclair, Michael B.; Tauke-Pedretti, Anna; Tauke-Pedretti, Anna; Warne, Larry K.; Warne, Larry K.; Wendt, J.R.; Wendt, J.R.; Beechem, Thomas E.; Beechem, Thomas E.; Howell, Stephen W.; Howell, Stephen W.; McDonald, Anthony E.; McDonald, Anthony E.; Ruiz, Isaac R.; Ruiz, Isaac R.

Abstract not provided.

Improved infrared detection using nanoantennas

International Conference on Optical MEMS and Nanophotonics

Peters, D.W.; Sinclair, Michael B.; Goldflam, Michael G.; Warne, Larry K.; Campione, Salvatore; Kim, Jin K.; Davids, Paul D.; Tauke-Pedretti, Anna; Wendt, J.R.; Klem, John F.; Hawkins, Samuel D.; Parameswaran, Sivasubramanian P.; Coon, W.T.; Keeler, G.A.; Fortune, Torben R.

We examine integration of a patterned metal nanoantenna (or metasurface) directly onto long-wave infrared detectors. These structures show significantly improved external quantum efficiency compared to their traditional counterparts. We will show simulation and experimental results.

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Planar Ohmic Contacts to Al 0.45 Ga 0.55 N/Al 0.3 Ga 0.7 N High Electron Mobility Transistors

ECS Journal of Solid State Science and Technology

Klein, Brianna A.; Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Sanchez, Carlos A.; Douglas, Erica A.; Crawford, Mary H.; Miller, Mary A.; Kotula, Paul G.; Fortune, Torben R.; Abate, Vincent M.

Here, we present a low resistance, straightforward planar ohmic contact for Al0.45Ga0.55N/Al0.3Ga0.7N high electron mobility transistors. Five metal stacks (a/Al/b/Au; a = Ti, Zr, V, Nb/Ti; b = Ni, Mo, V) were evaluated at three individual annealing temperatures (850, 900, and 950°C). The Ti/Al/Ni/Au achieved the lowest specific contact resistance at a 900°C anneal temperature. Transmission electron microscopy analysis revealed a metal-semiconductor interface of Ti-Al-Au for an ohmic (900°C anneal) and a Schottky (850°C anneal) Ti/Al/Ni/Au stack. HEMTs were fabricated using the optimized recipe with resulting contacts that had room-temperature specific contact resistances of ρc = 2.5 × 10-5 Ω cm², sheet resistances of RSH = 3.9 kΩ/$\blacksquare$, and maximum current densities of 75 mA/mm (at VGATE of 2 V). Electrical measurements from -50 to 200°C had decreasing specific contact resistance and increasing sheet resistance, with increasing temperature. These contacts enabled state-of-the-art performance of Al0.45Ga0.55N/Al0.3Ga0.7N HEMTs.

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High Temperature Operation of Al0.45Ga0.55N/Al0.30Ga0.70 N High Electron Mobility Transistors

ECS Journal of Solid State Science and Technology

Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Klein, Brianna A.; Douglas, Erica A.; Sanchez, Carlos A.; Fortune, Torben R.

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that have a bandgap greater than ~3.4 eV, beyond that of GaN and SiC, and are promising candidates for RF and power applications. Long-channel AlxGa1-xN HEMTs with x = 0.3 in the channel have been built and evaluated across the -50°C to +200°C temperature range. Room temperature drain current of 70 mA/mm, absent of gate leakage, and with a modest -1.3 V threshold voltage was measured. A very large Ion/Ioff current ratio, greater than 108 was demonstrated over the entire temperature range, indicating that off-state leakage is below the measurement limit even at 200°C. Finally, combined with near ideal subthreshold slope factor that is just 1.3× higher than the theoretical limit across the temperature range, the excellent leakage properties are an attractive characteristic for high temperature operation.

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Resonantly enhanced infrared detectors based on type-II superlattice absorbers

Goldflam, Michael G.; Goldflam, Michael G.; Campione, Salvatore; Campione, Salvatore; Kadlec, Emil A.; Kadlec, Emil A.; Hawkins, Samuel D.; Hawkins, Samuel D.; Coon, Wesley T.; Coon, Wesley T.; Fortune, Torben R.; Fortune, Torben R.; Parameswaran, Sivasubramanian P.; Parameswaran, Sivasubramanian P.; Keeler, Gordon A.; Keeler, Gordon A.; Klem, John F.; Klem, John F.; Tauke-Pedretti, Anna; Tauke-Pedretti, Anna; Shaner, Eric A.; Shaner, Eric A.; Davids, Paul D.; Davids, Paul D.; Warne, Larry K.; Warne, Larry K.; Wendt, J.R.; Wendt, J.R.; Kim, Jin K.; Kim, Jin K.; Peters, D.W.; Peters, D.W.

Abstract not provided.

Next-generation infrared focal plane arrays for high-responsivity low-noise applications

IEEE Aerospace Conference Proceedings

Goldflam, Michael G.; Hawkins, Samuel D.; Parameswaran, Sivasubramanian P.; Tauke-Pedretti, Anna; Warne, Larry K.; Peters, D.W.; Campione, Salvatore; Coon, W.T.; Keeler, Gordon A.; Shaner, Eric A.; Wendt, J.R.; Kadlec, Emil A.; Fortune, Torben R.; Klem, John F.; Davids, Paul D.; Kim, Jin K.

High-quality infrared focal plane arrays (FPAs) are used in many satellite, astronomical, and terrestrial applications. These applications require highly-sensitive, low-noise FPAs, and therefore do not benefit from advances made in low-cost thermal imagers where reducing cost and enabling high-temperature operation drive device development. Infrared detectors used in FPAs have been made for decades from alloys of mercury cadmium telluride (MCT). These infrared detectors are nearing the believed limit of their performance. This limit, known in the infrared detector community as Rule 07, dictates the dark current floor for MCT detectors, in their traditional architecture, for a given temperature and cutoff wavelength. To overcome the bounds imposed by Rule 07, many groups are working on detector compounds other than MCT. We focus on detectors employing III-V-based gallium-free InAsSb superlattice active regions while also changing the basic architecture of the pixel to improve signal-to-noise. Our architecture relies on a resonant, metallic, subwavelength nanoantenna patterned on the absorber surface, in combination with a Fabry-Pérot cavity, to couple the incoming radiation into tightly confined modes near the nanoantenna. This confinement of the incident energy in a thin layer allows us to greatly reduce the volume of the absorbing layer to a fraction of the free-space wavelength, yielding a corresponding reduction in dark current from spontaneously generated electron-hole pairs in the absorber material. This architecture is detector material agnostic and could be applied to MCT detector structures as well, although we focus on using superlattice antimonide-based detector materials. This detector concept has been applied to both mid-wave (3-5 μm) and longwave (8-12 μm) infrared detectors and absorbers. Here we examine long-wave devices, as these detectors currently have a larger gap between desired device performance and that of currently existing detectors. The measured structures show an external quantum efficiency exceeding 50%. We present a comparison of the modeled and measured photoresponse of these detectors and compare these detectors to currently available commercial detectors using relevant metrics such as external quantum efficiency. We also discuss modeling of crosstalk between adjacent pixels and its influence on the potential for a dual-wavelength detector. Finally, we evaluate potential advances in these detectors that may occur in the near future.

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Enhanced infrared detectors using resonant structures combined with thin type-II superlattice absorbers

Applied Physics Letters

Goldflam, Michael G.; Kadlec, Emil A.; Olson, B.V.; Klem, John F.; Hawkins, Samuel D.; Parameswaran, Sivasubramanian P.; Coon, W.T.; Keeler, Gordon A.; Fortune, Torben R.; Tauke-Pedretti, Anna; Wendt, J.R.; Shaner, Eric A.; Davids, Paul D.; Kim, Jin K.; Peters, D.W.

We examined the spectral responsivity of a 1.77 μm thick type-II superlattice based long-wave infrared detector in combination with metallic nanoantennas. Coupling between the Fabry-Pérot cavity formed by the semiconductor layer and the resonant nanoantennas on its surface enables spectral selectivity, while also increasing peak quantum efficiency to over 50%. Electromagnetic simulations reveal that this high responsivity is a direct result of field-enhancement in the absorber layer, enabling significant absorption in spite of the absorber's subwavelength thickness. Notably, thinning of the absorbing material could ultimately yield lower photodetector noise through a reduction in dark current while improving photocarrier collection efficiency. The temperature- and incident-angle-independent spectral response observed in these devices allows for operation over a wide range of temperatures and optical systems. This detector paradigm demonstrates potential benefits to device performance with applications throughout the infrared.

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An AlN/Al0.85Ga0.15N high electron mobility transistor

Applied Physics Letters

Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Douglas, Erica A.; Sanchez, Carlos A.; King, Michael P.; Coltrin, Michael E.; Fortune, Torben R.; Kaplar, Robert K.

An AlN barrier high electron mobility transistor (HEMT) based on the AlN/Al0.85Ga0.15N heterostructure was grown, fabricated, and electrically characterized, thereby extending the range of Al composition and bandgap for AlGaN channel HEMTs. An etch and regrowth procedure was implemented for source and drain contact formation. A breakdown voltage of 810 V was achieved without a gate insulator or field plate. Excellent gate leakage characteristics enabled a high Ion/Ioff current ratio greater than 107 and an excellent subthreshold slope of 75 mV/decade. A large Schottky barrier height of 1.74 eV contributed to these results. In conclusion, the room temperature voltage-dependent 3-terminal off-state drain current was adequately modeled with Frenkel-Poole emission.

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Minority carrier lifetime and dark current measurements in mid-wavelength infrared InAs0.91Sb0.09 alloy nBn photodetectors

Applied Physics Letters

Olson, B.V.; Kim, Jin K.; Kadlec, Emil A.; Klem, John F.; Hawkins, Samuel D.; Leonhardt, Darin L.; Coon, W.T.; Fortune, Torben R.; Cavaliere, Melissa A.; Tauke-Pedretti, Anna; Shaner, Eric A.

Carrier lifetime and dark current measurements are reported for a mid-wavelength infrared InAs0.91Sb0.09 alloy nBn photodetector. Minority carrier lifetimes are measured using a non-contact time-resolved microwave technique on unprocessed portions of the nBn wafer and the Auger recombination Bloch function parameter is determined to be |F1F2|=0.292. The measured lifetimes are also used to calculate the expected diffusion dark current of the nBn devices and are compared with the experimental dark current measured in processed photodetector pixels from the same wafer. Excellent agreement is found between the two, highlighting the important relationship between lifetimes and diffusion currents in nBn photodetectors.

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Wafer-level step-stressing of InGaP/GaAs HBTs

ECS Transactions

Baca, A.G.; Kotobi, Joshua A.; Fortune, Torben R.; Gorenz, Alan G.; Klem, John F.; Briggs, R.D.; Clevenger, Jascinda C.; Patrizi, G.A.

Wafer-level step-stress experiments on high voltage Npn InGaP/GaAs HBTs are presented. A methodology utilizing brief, monotonically increasing stresses and periodic, interrupted parametric characterization is presented. The method and various examples of step-stressed HBTs illustrate the value of the technique for screening the reliability of HBT wafers. Degradation modes observed in these InGaP/GaAs HBTs closely correspond to a subset of those in other, longer types of reliability experiments and can be relevant in a reliability screen. A statistical sampling of HBT wafers reveals a consistently realized critical destructive limit over a very narrow power range, which indicates that thermal stress is the main cause of degradation. When stepped just shy of the destructive limit, electrical characteristics are capable of revealing gradual degradation. The end state of stressing typically involves shorting of both the base-emitter and base-collector junctions. Interrupted characterization revealed cases where baseemitter shorts preceded base-collector shorts and other cases where base-collector shorts occurred first. Examples of degradation include reductions in reverse breakdown voltage, increases in the offset voltage, and drops in current gain. These wafer-level stepstress techniques show promise for reducing the large time lag between wafer fabrication and useful reliability screening in HBTs.

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39 Results
39 Results