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![Transport in ZnO
Dave Look, Wright State
•[VZn ] = 1.7x1020
Pulse Laser cm-3 gives
32 Deposition E(formation) =
in Ar 0.2 eV; provides
accurate check
30
Mobility (cm /V s)
on theory (DFT)
µ (ND, NA, m*, T) •Reduced [VZn ]
2
Fitting parameters: m* with Zn anneals:
28 21 -3 0.30 got = 1.4x10-4
ND = 1.45 x 10 cm SIMS
20 -3
-cm, 3rd best in
NA = 1.71 x 10 cm Positron 0.34 world
26 m* = 0.34m0 Kane model •Future: create
0.40 GaZn donors by
filling VZn with Ga
24 •Future: apply
0 100 200 300 methods to other
TMOs
T (K)
DISTRIBUTION A: Approved for public release; distribution is unlimited. 15](https://image.slidesharecdn.com/1-hwang-ghz-thzelectronics-120713095140-phpapp02/85/Hwang-GHz-THz-Electronics-Spring-Review-2012-15-320.jpg)
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Hwang - GHz-THz Electronics - Spring Review 2012
The document outlines advancements and challenges in GHz-THz electronics research, focusing on material and device breakthroughs for transistors using both conventional and novel semiconductors. It highlights key areas such as THz electronics, novel GHz electronics, and reconfigurable electronics, with discussion on various applications and the need for improved crystalline structures, purity control, and understanding of nanometer-scale interactions. The report emphasizes collaboration among various organizations to explore new technologies and improve semiconductor performance.
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Hwang - GHz-THz Electronics - Spring Review 2012
- 1. GHz-THz Electronics 08 MAR 2012 Jim Hwang Program Manager AFOSR/RSE Integrity Service Excellence Air Force Research Laboratory 15 February 2012 DISTRIBUTION A: Approved for public release; distribution is unlimited. 1
- 2. 2012 AFOSR SPRINGREVIEW NAME: Jim Hwang BRIEF DESCRIPTION OF PORTFOLIO: GHz-THz Electronics LIST SUB-AREAS IN PORTFOLIO: I. THz Electronics – Material and device breakthroughs for transistors based on conventional semiconductors (e.g., group IV elements or group III-V compounds with covalent bonds) to operate at THz frequencies with adequate power. Challenges exist mainly in perfecting crystalline structure and interfaces. II. Novel GHz Electronics – Material and device breakthroughs for transistors based on novel semiconductors (e.g., transition-metal oxides with ionic bonds) to operate at GHz frequencies with high power. Challenges exist mainly in controlling purity and stoichiometry, as well as in understanding doping/transport. III. Reconfigurable Electronics – Material and device breakthroughs for meta-materials, artificial dielectrics, ferrites, multi-ferroics, nano-magnetics, and micro/nano electromechanical systems to perform multiple electronic, magnetic and optical functions. Challenges exist mainly in understanding the interaction between electromagnetic waves, electrons, plasmons and phonons on nanometer scale. DISTRIBUTION A: Approved for public release; distribution is unlimited. 2
- 3. I. THz Electronics • Sub-millimeter-wave radar & imaging • Space situation awareness • Chemical/biological/nuclear sensing • Ultra-wideband communications X’tal Reliability • Ultra-high-speed on-board and AFOSR front-end data processing DARPA ONR III-N THz ONR DEFINE DARPA (Power) Intel IBM THz Cutoff Frequency DISTRIBUTION A: Approved for public release; distribution is unlimited. 3
- 4. Intel’s High-k FinFETs Development Production Gate S Stack Q k 0 Drain C Source e V d Channel DISTRIBUTION A: Approved for public release; distribution is unlimited. 4
- 5. Challenges for THzElectronics •Highly strained growth •Single-phase ternary •P doping DISTRIBUTION A: Approved for public release; distribution is unlimited. 5
- 6. Covalent Semiconductors Covalent Semiconductors DISTRIBUTION A: Approved for public release; distribution is unlimited. 6
- 7. InAlN Molecular BeamEpitaxy Jim Speck, UC Santa Barbara Cross-sectional transmission electron Scanning transmission electron X-ray diffraction confirms lattice match microscopy reveals columnar structure microscopy shows nano-network 17% In mole fract. 140nm thickness GaN peak •First extensive study of phase separation in nitrides •Nano-network may be useful for thermoelectrics •Homogeneous InAlN grown by NH3 MBE and MOCVD perhaps by suppressing In ad-layer at higher growth temperatures Atomic probe confirms composition variation DISTRIBUTION A: Approved for public release; distribution is unlimited. 7
- 8. P-Doped InGaN Alan Doolittle, Georgia Tech Objective: P-type GaN or InGaN for HBT Approach: Optimize MBE temperature and flux to prevent surface segregation/decomposition & to provide optimum Mg substitutional sites Results: Breakthrough in single-phase, high-quality InGaN doped with GaN 1020/cm3 Mg and >50% temperature-independent activation Plan: Mitigate electrical leakage via metal-decorated dislocations GaN In0.2Ga0.8N GaN GaN In0.4Ga0.6N Constant resistivity when GaN GaN:Mg doped 1019/cm3 DISTRIBUTION A: Approved for public release; distribution is unlimited. 8
- 9. Hot Electrons/Phonons inGaN Hadis Morkoc, Virginia Commonwealth Objective: Optimize electron density Resonance Approach: Understand interaction of hot Plasmon electrons and phonons Result: Explained limits of many GaN devices Plan: Dual-well channel Power Supply 2700K Electrons Optimum electron 2400K concentration for I ~ nv Acoustic Velocity Peak optical plasmon resonance phonons phonons and optical-acoustic phonon decay 300K heat sink DISTRIBUTION A: Approved for public release; distribution is unlimited. 9
- 10. Limit of AlN/GaNHEMTs Grace Xing & Debdeep Jena, Notre Dame Speed (GHz) Objective: THz AlN/GaN HEMTs 600 Approach: Outlined below 400 Results: 370GHz cutoff frequency HRL MIT Plan: Verify/improve phonon- 200 NiCT limited velocity model Notre Dame Year 2007 ‘09 ‘10 ‘11 ‘12 Regrown contact with Rs<0.1Ω-mm Reduce Control gate length surface states Increase 2DEG mobility Add AlN back barrier DISTRIBUTION A: Approved for public release; distribution is unlimited. 10
- 11. II. Novel GHzElectronics Breakdown, Power Nano-Oxide X’tal Reliability AFOSR AFOSR MESO ZnO MOSFET DARPA DARPA Extreme E ONR III-N THz ONR DEFINE ONR Coupled Φ ONR DARPA Interact TI Intel IBM ARO Rad-Hard E DTRA DMR NSF Cutoff Frequency Thin-Film E Industry DISTRIBUTION A: Approved for public release; distribution is unlimited. 11
- 12. Ionic vs. CovalentSemiconductors Covalent • Transparent Electronics: ZnO, MgO, InGa3Zn5O5 Semiconductors • Heterojunctions: MgZnO/ZnO, LaAlO3/SrTiO3 • Multiferroics: BiFeO3, EuO, • Metal-Insulator Transition: VO2, SmNiO3, NdNiO3, • Topological Insulators: Bi2Se3, Bi2Te3, Bi1-xSex, • Other Chalcogenides: sulfides, selenides, tellurides DISTRIBUTION A: Approved for public release; distribution is unlimited. 12
- 13. Challenges for THzElectronics •Highly strained growth •Single-phase ternary •P doping DISTRIBUTION A: Approved for public release; distribution is unlimited. 13
- 14. Merits of IonicSemiconductors • Less demanding on crystalline perfectness Challenges • Deposition on almost any substrate at low temp. •Composition and • Radiation hard, fault tolerant, self healing • High electron concentration with correlated transport purity control Mobility • Metal-insulator transition with high on-off ratio •Transport not well • Wide bandgap for high power and transparency • Topological effects understood • SWAP-C and conforming Covalent Semiconductor Ionic Covalent Ionicity Ionic Semiconductor DISTRIBUTION A: Approved for public release; distribution is unlimited. 14
- 15. Transport in ZnO Dave Look, Wright State •[VZn ] = 1.7x1020 Pulse Laser cm-3 gives 32 Deposition E(formation) = in Ar 0.2 eV; provides accurate check 30 Mobility (cm /V s) on theory (DFT) µ (ND, NA, m*, T) •Reduced [VZn ] 2 Fitting parameters: m* with Zn anneals: 28 21 -3 0.30 got = 1.4x10-4 ND = 1.45 x 10 cm SIMS 20 -3 -cm, 3rd best in NA = 1.71 x 10 cm Positron 0.34 world 26 m* = 0.34m0 Kane model •Future: create 0.40 GaZn donors by filling VZn with Ga 24 •Future: apply 0 100 200 300 methods to other TMOs T (K) DISTRIBUTION A: Approved for public release; distribution is unlimited. 15
- 16. ZnO Thin-Film Transistors Burhan Bayraktaroglu, AFRL/RYDD Objective: Exploit unique electronic PLD Grain properties of nanocrystalline ZnO films Boundaries Approach: • Theoretical doping & mobility models • Pulsed laser deposition (PLD) • Ga doping in Ar at low temperatures Nanocrystalline World’s 1st microwave thin-film transistor ZnO Plan Record Performance •Room-temp. 150°C deposition deposition 110 cm2/V.s electron mobility •High-k gate 875mA/mm current density insulator 9.5W/mm dc power density •MgZnO/ZnO 1012 on/off ratio hetero- 60mV/dec sub-threshold slope junction 10 GHz cut-off frequency LG=1.2m DISTRIBUTION A: Approved for public release; distribution is unlimited. 16
- 17. Correlated Oxide Field-EffectDevices Shriram Ramanathan, Harvard Objective: Fundamental understanding of field-effect MBE switches utilizing ultra-fast (ps) reversible metal- Estimated power-delay SmNiO3 insulator (Mott) transition in correlated oxides Approach: Fabricate field-effect transistors with oxide channels and investigate device characteristics product Result: High-quality SmNiO3 grown by molecular- VO2 Mott FET beam epitaxy on LaAlO3 for room-temperature transition vs. Si MOSFET Plan: Electronic transport measurement on thin-film LaAlO3 hetero-junctions of different oxides Temperature (°C) DISTRIBUTION A: Approved for public release; distribution is unlimited. 17
- 18. III. Reconfigurable Electronics •Multipleelectronic, magnetic and optical functions for UAV/MAV •Meta-materials, artificial dielectrics, ferrites, multi-ferroics, nano-magnetics, MEMS/NEMS Challenges: Understand interaction between electromagnetic waves, electrons, plasmons and phonons on nm scale DISTRIBUTION A: Approved for public release; distribution is unlimited. 18
- 19. EuO-Based Multiferroics Darrell Schlom, Cornell 1 Normalized Magnetization (a.u.) Objective: Enhance and Ferromagnetic exploit exceptional 5% Gd-doped spintronic, optical, and Paramagnetic magnetic properties of 0.5 EuO, including highest 5% Lu-doped ∆R/R of any metal-insulator transition, greatest spin- 5% La-doped = 0.6eV splitting of any semiconductor, and 2nd 0 20 40 60 80 100 120 140 highest of spin Temperature (K) polarization. Approach: Reduce defects in EuO films to enable Insulator Andreev reflection of controlled doping. Metal >96% spin-polarized Combine strain and doping carriers from EuO to Nb to boost Curie temperature. Results: Demonstrated controlled rare-earth doping of EuO. Plan: Apply misfit strain to boost Curie temperature DISTRIBUTION A: Approved for public release; distribution is unlimited. 19
- 20. Topological Insulators Yoichi Ando, Osaka U. Phenomena: • Insulating bulk with metallic surface • Massless Dirac fermions high-mobility transistor • Dissipationless spin current Low-loss spintronics Objectives: • To explore novel physics • To minimize bulk current Unexpected • To discover better TI materials mass • To detect surface spin currents acquisition of Approaches: Dirac fermions • Explore ternary chalcogenides • Fabricate TI-ferromagnet devices on TlBi(S,Se)2 • Precise transport measurements DISTRIBUTION A: Approved for public release; distribution is unlimited. 20
- 21. Collaboration • AFOSR • Kitt Reinhardt – Eletro-thermal/thermo-electric effects • Gernot Pomrenke – THz optics, microwave photonics, reconfigurable electronics • Harold Weinstock – Nanoscale oxides, spintronics • Seng Hong (AOARD) – Osaka U. • Scott Dudley (EOARD) – SPI Lithuania • ONR • Dan Green – >95% overlap of interest • Paul Maki – GaN • ARO • Marc Ulrich – Physics of topological insulators • DARPA • Jeff Rogers – Topological insulator devices • John Albrecht – THz electronics, GaN • Bill Chappell – Adaptive RF technology, RF-FPGA • DTRA • Don Silversmith – Rad-hard electronics • Tony Esposito & Kiki Ikossi – THz applications • NSF • Samir El-Ghazaly – THz electronics • Anu Kaul – 2D materials & devices beyond graphene DISTRIBUTION A: Approved for public release; distribution is unlimited. 21
- 22. Take Away Messages I.Covalent Semiconductors • Transition bulk growth and reliability projects via STTRs • Push to THz via highly-strained thin-film growth, surface High-k Gate passivation, and high-k gate stack Complex Oxides II. Ionic Semiconductors • Push oxide electronics to high GHz range • Emphasize thin-film heterostructures Oxide Electronics • Explore extreme carrier concentration • Understand and overcome mobility limitation • Explore metal-insulator transition & topological insulators III. Reconfigurable Electronics • Buildup program next year Multi-Ferroics DISTRIBUTION A: Approved for public release; distribution is unlimited. 22