Jan. 4, 2007 Engineers at UC San Diego have synthesized a long-
sought semiconducting material that may pave the way for an
inexpensive new kind of light emitting diode (LED) that could
compete with today's widely used gallium nitride LEDs, according
to a new paper in the journal Nano Letters. To build an LED, you
need both positively and negatively charged semiconducting
materials; and the engineers synthesized zinc oxide (ZnO)
nanoscale cylinders that transport positive charges or "holes"
-- so-called "p-type ZnO nanowires." They are endowed with a
supply of positive charge carrying holes that, for years, have
been the missing ingredients that prevented engineers from
building LEDs from ZnO nanowires. In contrast, making "n-type"
ZnO nanowires that carrier negative charges (electrons) has not
been a problem. In an LED, when an electron meets a hole, it
falls into a lower energy level and releases energy in the form
of a photon of light. Deli Wang, an electrical and computer
engineering professor from UCSD's