Group IV Nano Optoelectronics: Si Nano Optoelectronics: Recent Developments based on Bottom-Up Approaches Recent Developments based on Bottom-Up Approaches The 6 th US-Korea Forums on Nanotechnology: Nanoelectronics and its Integration with Applications April 29. 2009 Moon-Ho Jo Dept. of Materials Science and Engineering Pohang University of Science and Technology (POSTECH) US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
2H 2 2H (Vapor) (Vap or) SiH SiH 4 SiGe (Solid) (Solid) (Liquid) (Liquid) GeH GeH 4 Bottom-Up Nanowires for Integrated Nanosystems? Bottom-Up Nanowires for Integrated Nanosystems? US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Nanowire Photonics/Optoelectronics/Photovoltaics 1. Unique size effects at 1. Unique size effects at the individual NW the individual NW level level 2. Large-area integrated 2. Large-area integrated NW arrays NW arrays US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Nano Device Materials & Physics Laboratory Nanowire Photonics/Optoelectronics/Plasmonics Nature Phys., Accepted (2009) Nano Lett., Accepted (2009) Appl. Phys. Lett., In Press (2009) [Ultraviolet] Appl. Phys. Lett., 92 263111 (2008) 1.55 μ m 1.35 μ m [Near Infrared] [Visible] Nano Lett. 6 2679 (2006) SiO 2 /Si Nanowire Growth Submitted, (2009) Nano Lett. 8 431 (2008) Adv. Mater. 20 4684 (2008) Chem. Mater 20 6577 (2008) Appl. Phys. Lett., 91, 223107 (2007) Adv. Mater., 19, 3637 (2007) Appl. Phys. Lett. 88, 193105 (2006) Nano Lett. 4 1547 (2004) 0.209nm 0.209nm 0.209nm 20 nm 20 nm 20 nm 2 nm 2 nm 2 nm 2 nm Nanowire Electronics Nano Lett. 8 4523 (2008) Appl. Phys. Lett., 91, 033104 (2007) Nano Lett, 6 2014 (2006) US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Nano Si Photonics Si Quantum Dot Photonics Photoluminescence in NIR to UV from Si quantum dots (QD) of various size * T.Y. Kim et al., Appl. Phys. Lett . 85 85, 5355 (2004) Lorenzo Pavesi and David J. Lockwood, Materials Today , Jan. 26, 2005 • Exciton-Bohr radius of Si is ~5nm. (~18nm for Ge) • Because of (possible) quantum confinements, Si QDs smaller than 5nm, can emit light from the near infrared throughout the visible with quantum efficiencies in excess of 10%. • Radiative transition rates increase due to the confinement of e - h pairs. US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Nano Silicon Photovoltaics Multiple Exciton Generation in Si Quantum Dots M.C. Beard, Nano. Lett . 7, 2506 (2007) • Multiple bound e - h pairs (excitons) can be generated in Si nanocrystals (9.5 nm) upon photon absorption of energy greater than twice the band gap. • The exciton production quantum was found to be 2.6 excitons per absorbed photon at 3.4E g . US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Si:Ge Nanowire Optoelectronics Si:Ge Nanowire Optoelectronics Si:Ge Nano Crystals: The model system for continuously varying lattices and energy band-gaps at the nanometer scale 1. Nanowires: Electrically driven Efficient Light-Emitting/Detecting Devices 2. Si:Ge Alloys: Tunable Energy upon Light-Matter Interaction US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Growth of Single-Crystalline Si 1-x Ge x Nanowires Vapor-Liquid-Solid (VLS) Nanowire Growth Conventional VLS-CVD Nanowire Growth • Catalyst-assisted CVD of group IV semiconductor nanowires: - Sources: SiH 4 and GeH 4 2 μ m 5nm - Dopants: PH 3 and B 2 H 6 Chang-Beom Jin et al., Appl. Phys. Lett . 88 88, 193105 (2006) Jee-Eun Yang, et al., Nano Lett. 6, 2679 (2006) (Vapor) (Vapor) 2H 2 SiH 4, GeH 4 (Solid) (S olid) Si (Liqui (Li quid) d) US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Band-Gap Modulation in Si 1-x Ge x Nanowires Si 1-x Ge x Nanowire Crystals: Optical Band-Edge Absorption Jee-Eun Yang et al., Nano Lett. 6, 2679 (2006) • The optical band-edge of 0.68eV and 1.05eV for Ge and Si nanowires, and these values agree with the energy band-gaps of bulk Ge and Si crystals of 0.65eV and 1.12eV. • The optical band-edge in various Si 1-x Ge x nanowires systematically shifts from that of Si nanowires to that of Ge nanowires with increasing Ge content. • We observed strong blue-shift of optical band-edge for thinner nanowires whose diameter is smaller than 10nm. (Exciton- Bohr radius of 4.7nm for Si and 17.7nm for Ge) US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Nano Optoelectronics Laboratory Spatially Resolved Optoelectronic Measurements 532 nm Laser λ Diffraction limit : Δ = × = 360 nm, 650 nm R k N . A . k : technical constant (~0.61) N. A. : numerical aperture (0.5, 0.9) • A new experimental setup based on a scanned laser confocal microscope allows combined measurements of “spatially resolved” electroluminescence and photoconductivity. • The setup also allows the “spectral measurements” of electroluminescence and correlated photon counting. • With the addition of an ultrafast laser, it should also allow “time-resolved measurements”. US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Intra-Nanowire p - n diode Photocurrent in Si Nanowire p - n diode D D S S 100 V sd = 5.0 V V b n 0 V sd = 2.5 V p V sd = 0.0 V 2um e V sd = -2.5 V h ν Drai Drain Sourc ource V sd = -5.0 V h -300 n p nA Cheol-Joo Kim et al., Nano Lett ., Accepted (2009) US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Raman Scattering in Si 1-x Ge x Semiconductors Confocal Raman Spectro-Microscopy Jee-Eun Yang et al., Appl. Phys. Lett ., 92 92, 263111 (2008) (with Prof. Zee Hwan Kim, Korea Univ. ) US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Ge Nanowire Photodetector Cheol-Joo Kim et al., Nano Lett ., Accepted (2009) Ge NW -7 10 Si NW Laser 0.73 -8 Δ G (S) 10 532 nm -9 10 Photodiode 0.32 0.87 -10 10 Objective Lens (N.A. 2 3 4 5 6 =0.5 ) 10 10 10 10 10 2 ) Intensity (W/cm Ge NW Si NW or Ge NW Si NW -5 10 Y PC Gain A V sd -6 10 V g X XY piezo-scanner -7 10 2 3 4 5 6 10 10 10 10 10 2 ) Intensity (W/cm - The PC for Ge NWs is more than two orders of magnitude higher than that of Si NWs. This PC enhancement in Ge NWs is even more pronounced at lower light intensity. - Ge NW can be an excellent candidate for polarization-sensitive nanoscale photodetectors especially in the visible range. - Ge NWs show extremely sensitive photoresponse especially at a low intensity regime, which is attributed to the internal gain mechanism, originating from the surface state filling. US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Epitaxial NW Growth for Ordered Arrays Cheol-Joo Kim et al., Appl. Phys. Lett ., In Press (2009) Kibum Kang et al ., Adv. Mater . 20 4684 (2008) Vertical Growth by Epitaxy on (111) Si Substrates 10 μ m (a) (b) (c) Substrate Nanowire 20 μ m 50 nm 2 nm US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Epitaxial NW Growth for Ordered Arrays (I) PS Nanosphere (I) PS Nanosphere Lithography Lithography Substrate: SiO 2 (100 nm)/Si(111)- Substrate: SiO (100 nm)/Si(111)- p Reactive ion etching Reactive ion etching Metal deposition Metal deposition & PS lift-off & PS lift-off SiO SiO 2 Dry & y & W Wet etchi t etching Au deposition Au deposition Growth of Si NWs Growth of Si NWs & Lift-off & Lif -off Si(111) Si(111) SiO SiO 2 Metal Metal PS PS Au Au US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Templated-Assisted NW Growth for Ordered Arrays Si Nanowire Arrays from Au-Catalyst Patterns by Nanosphere Lithography US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Si NW Li-Battery at POSTECH (1) Si nanowire vs. NiSi nanowire • World-record Capacity and Efficiency (charging/discharging) up to 4,000 and 99 %! • Capacity fading is still small and is maintained up to 80 % after 50 cycles ! e - Discharge Discharge Charge Charge LOAD Si NW Anode Anode Anode Li Cathode Electrolytes Potentiostat/Galvanostat US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
N ANO ANO D D EVI M ATERIALS ATERIALS & Physics L & Physics L AB & Physics L N E M & Physics L ANO EVI EVICE ATERIALS AB AB ANO EVICE E ATERIALS AB Jee-Eun Yang Hyun-Seung Lee Cheol-Joo Kim Kibum Kang US-Korea Nano-Forum 2009 POSTECH, Nano Device Materials and Physics Lab
Recommend
More recommend
