1 research outputs found
Polarization-Induced pn Diodes in Wide-Band-Gap Nanowires with Ultraviolet Electroluminescence
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