Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Cheaper LEDs from breakthrough in zinc oxide (ZnO) nanowire research

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 Jacobs School of Engineering, and colleagues at UCSD and Peking University, report synthesis of high quality p-type zinc oxide nanowires in a paper published online by the journal Nano Letters.

"Zinc oxide nanostructures are incredibly well studied because they are so easy to make. Now that we have p-type zinc oxide nanowires, the opportunities for LEDs and beyond are endless," said Wang.

Wang has filed a provisional patent for p-type ZnO nanowires and his lab at UCSD is currently working on a variety of nanoscale applications.

"Zinc oxide is a very good light emitter. Electrically driven zinc oxide single nanowire lasers could serve as high efficiency nanoscale light sources for optical data storage, imaging, and biological and chemical sensing," said Wang.

To make the p-type ZnO nanowires, the engineers doped ZnO crystals with phosphorus using a simple chemical vapor deposition technique that is less expensive than the metal organic chemical vapor deposition (MOCVD) technique often used to synthesize the building blocks of gallium nitride LEDs. Adding phosphorus atoms to the ZnO crystal structure leads to p-type semiconducting materials through the formation of a defect complex that increases the number of holes relative to the number of free electrons.

"Zinc oxide is wide band gap semiconductor and generating p-type doping impurities that provide free holes is very difficult – particularly in nanowires. Bin Xiang in my group worked day and night for more than a year to accomplish this goal," said Wang.

The starting materials and manufacturing costs for ZnO LEDs are far less expensive than those for gallium nitride LEDs. In the future, Wang expects to cut costs even further by making p-type and n-type ZnO nanowires from solution.

For years, researchers have been making electron-abundant n-type ZnO nanowire crystals from zinc and oxygen. Missing oxygen atoms within the regular ZnO crystal structure create relative overabundances of zinc atoms and give the semiconductors their n-type, conductive properties. The lack of accompanying p-type ZnO nanowires, however, has prevented development of a wide range of ZnO nanodevices.

While high quality p-type ZnO nanowires have not previously been reported, groups have demonstrated p-type conduction in ZnO thin films and made ZnO thin film LEDs. Using ZnO nanowires rather than thin films to make LEDs would be less expensive and could lead to more efficient LEDs, Wang explained.

Having both n- and p-type ZnO nanowires – complementary nanowires – could also be useful in a variety of applications including transistors, spintronics, UV detectors, nanogenerators, and microscopy. In spintronics applications, researchers could use p-type ZnO nanowires to make dilute magnetic semiconductors by doping ZnO with magnetic atoms, such as manganese and cobalt, Wang explained.

Transistors that rely on the semiconducting properties of ZnO are also now on the horizon. "P-type doping in nanowires would make complementary ZnO nanowire transistors possible," said Wang.

Daniel Kane | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Gamma ray camera offers new view on ultra-high energy electrons in plasma
28.10.2016 | American Physical Society

nachricht Scientists measure how ions bombard fusion device walls
28.10.2016 | American Physical Society

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel light sources made of 2D materials

Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.

So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Prototype device for measuring graphene-based electromagnetic radiation created

28.10.2016 | Power and Electrical Engineering

Gamma ray camera offers new view on ultra-high energy electrons in plasma

28.10.2016 | Physics and Astronomy

When fat cells change their colour

28.10.2016 | Life Sciences

More VideoLinks >>>