Journal
NANO LETTERS
Volume 12, Issue 2, Pages 915-920Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl203982p
Keywords
Nanostructures; nitrides; molecular beam epitaxy; light-emitting diode; polarization; ultraviolet emission
Categories
Funding
- Office of Naval Research [N00014-09-1-1153]
- National Science Foundation [DMR-1055164, 2011101708]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [820414] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1055164] Funding Source: National Science Foundation
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Almost all electronic devices utilize a pn junction formed by random doping of donor and acceptor impurity atoms. We developed a fundamentally new type of pn junction not formed by impurity-doping, but rather by grading the composition of a semiconductor nanowire resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlGaN nanowires from 0% to 100% and back to 0% Al, we show the formation of a polarization-induced pn junction even in the absence of any impurity doping. Since electrons and holes are injected from AlN barriers into quantum disk active regions, graded nanowires allow deep ultraviolet LEDs across the AlGaN band-gap range with electroluminescence observed from 3.4 to 5 eV. Polarization-induced p-type conductivity in nanowires is shown to be possible even without supplemental acceptor doping, demonstrating the advantage of polarization engineering in nanowires compared with planar films and providing a strategy for improving conductivity in wide-band-gap semiconductors. As polarization charge is uniform within each unit cell, polarization-induced conductivity without impurity doping provides a solution to the problem of conductivity uniformity in nanowires and nanoelectronics and opens a new field of polarization engineering in nanostructures that may be applied to other polar semiconductors.
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