National Science Foundation Sb-doped SnO 2 as a transparent contact on InGaN/GaN LEDs James S....
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National Science Foundation Sb-doped SnO 2 as a transparent contact on InGaN/GaN LEDs James S. Speck, University of California-Santa Barbara, DMR 0909203 Outcome UCSB researchers have demonstrated Sb-doped SnO 2 (ATO) epitaxial contacts on GaN- based LEDs with equal performance to Sn-doped In 2 O 3 (ITO) contacts Impact Tin is relatively abundant and low cost compared to Indium ATO should also have better optical transparency than ITO Explanation High performance ATO contacts were realized via optimized epitaxial growth conditions on high performance GaN LED
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Transcript of National Science Foundation Sb-doped SnO 2 as a transparent contact on InGaN/GaN LEDs James S....
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Sb-doped SnO2 as a transparent contact on InGaN/GaN LEDs
James S. Speck, University of California-Santa Barbara, DMR 0909203Outcome UCSB researchers have demonstrated Sb-doped SnO2
(ATO) epitaxial contacts on GaN-based LEDs with equal performanceto Sn-doped In2O3 (ITO) contacts
Impact Tin is relatively abundantand low cost compared to IndiumATO should also have better optical transparency than ITO
Explanation High performance ATOcontacts were realized via optimizedepitaxial growth conditions on high performance GaN LED wafers.The ATO resistivity was 3.4x10-3 Ωcm
Fig. (a) optical image of 290×490 µm2 fabricated LEDs and TLM patterns;(b) the cross-section of the LEDstructure, (c) I-V curves for InGaN/GaN LEDs fabricatedwith ITO and ATO contacts
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High quality In2O3 for transparent electronics James S. Speck, University of California-Santa Barbara, DMR 0909203
Outcome Demonstration of record mobilityin In2O3 thin films via MBE on foreign substrates
Impact Demonstrates potential In2O3 as afor advanced devices when bulk In2O3 substrates are used for growth. Our partners at theInstitue for Crystal Growth (IKZ) in Berlinhave now demonstrated bulk In2O3 substrates.
Explanation Binary oxides - prepared withhigh quality and purity - are promising wide bandgapsemiconductors for future electron devices. Lower quality and purity forms of these oxides areused as transparent contact for LEDs,displays and solar cells, and as chemicalsensors.This work demonstrates how In2O3 can be prepared with high structural [1] and electrical [2] quality. High structural quality, such as a smooth surface, isnecessary for most device technologies,whereas high electrical quality (e.g. highmobilities) ensure high device performance.The high material quality allows investigation ofintrinsic material properties (doping, transport, opticalproperties …).
[1] O. Bierwagen and J.S. Speck, J. Appl. Phys.107, 113519 (2010).[2] O. Bierwagen and J.S. Speck, Appl. Phys. Lett. 97, 072103 (2010).
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Materials World Network: Growth and Characterization of Bulk Crystals and Epitaxial Films of Beta-Ga203, SnO2, In203 and ZnOJames S. Speck, University of California-Santa Barbara, DMR 0909203
Second joint UCSB-Humboldt University-IKZ Focused WorkshopHeld at IKZ (Adlershof, Berlin, Germany) – October 13-14, 2011
The second focused workshop onsemiconducting oxides was held atIKZ in October 2011.
Participants came from the German and US project partners UCSB(Jim Speck’s group), Institute of CrystalGrowth, Berlin (IKZ), and HumboldtUniversity, Berlin and from severalother institutes and universities.
The fifteen contributions by professors,postdocs, and graduate students dealtwith the preparation (both, bulk and thinfilms) and the properties (theory andexperiment) of semiconducting oxides.The moderate number of contributionsand participants allowed for in-depthdiscussion in an informal atmosphere,which strengthened existing- andestablished new collaborations amongthe participants.
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Studies of Surface Fermi Level in In2O3 and SnO2
James S. Speck, University of California-Santa Barbara, DMR 0909203
Surface Fermi Level from XPS(left) panels: In2O3 as-grown and after plasma oxidation(right) panel: SnO2 doped: Sb; undoped; In
Outcome Demonstration control ofsurface Fermi level in semiconductingoxides: In2O3 and SnO2
Impact Demonstrates that the surface accumulation layer can be controlledvia light surface damage or bulk doping
Explanation Binary oxides - prepared withhigh quality and purity - are promising wide bandgap semiconductors for future electron devices. One common feature of wide bandgap semiconducting oxides is the propensityfor a surface electron accumulation layer –SEAL (also responsible for gasand liquid sensing properties)
This work demonstrates how the SEAL inIn2O3 can be eliminated with light plasmatreatments [1] and how the SEAL in SnO2 canbe controlled with bulk doping [2]. These results come from careful XPS studies at UCSB and NIMS (at Spring8) on UCSB MBE-grown semiconducting oxides.
[1] O. Bierwagen et al., Appl. Phys.Lett. 98, 172101 (2011).[2] T. Nagata et al., Appl. Phys. Lett. 98, 232107 (2011).
