news digest ♦ LEDs
“We are very pleased to join I2BF Global Ventures and IP Group in this funding round, which will enable Seren to continue its impressive development of its LED technology. We remain confident that Seren can make a significant contribution to enabling the use of LEDs in a variety of different energy efficient applications where there is a continuous need to reduce power consumption and improve product performance. With this funding in place we look forward to the Company securing further deals for the use of its technology internationally.”
Meaglow InN wafers are nitrogen rich
Scientists from the firm have found that low temperature growth encourages nitrogen incorporation in indium nitride Meaglow says it has made a breakthrough in understanding the compound semiconductor indium nitride.
The material was grown by a plasma based technique known as RPECVD.
How the excess nitrogen could occur remained largely unexplained until now.
“Basically the excess nitrogen is seen when forming the material at relatively low temperatures using plasma based nitrogen sources. These plasma sources provide the extra potential energy needed for nitrogen rich material to form. To a greater, or lesser, extent excess nitrogen species are probably present in most InN samples, as plasma techniques are commonly used,” says Butcher. “It may take some years for the research community to come to terms with this, but nitrogen rich InN is a reality, and now it’s a reality we understand.”
InN wafers grown by Meaglow
Indium nitride (InN) when alloyed with GaN forms the light emitting component that powers a greater than $10 billion dollar LED industry.
In its own right, InN is being developed as an advanced material for solar cells, high speed transistor devices and other applications. However the material is still very mystifying.
For instance, based on theory it had long been assumed that it simply wasn’t possible to produce nitrogen rich InN. So it was a surprise a few years ago, when samples made at low temperatures were measured with greater than 30% excess nitrogen present.
How could this be?
Many researchers didn’t believe the measurements, though they were subsequently repeated by many groups. Theory didn’t seem to agree with experiment.
Now, scientists at Ontario-based Meaglow have used a technique called Heavy Ion Elastic Recoil Detection Analysis, or HIERDA, to determine the nitrogen to indium ratio in InN grown at different temperatures. This is a very accurate stoichiometry measurement technique and the graph below illustrating the
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www.compoundsemiconductor.net April/May 2012
Patented Migration Enhanced Afterglow (MEAglow) Reactor that grows the InN wafer
Meaglow is based in Thunder Bay, Ontario, Canada and produces a range of epitaxy equipment and MBE and MOCVD accessories, and also provides specialised thin films.
Nitrogen rich InN may also be important from another perspective. InN is plagued by a surface current problem which is limiting its development. However, the excess nitrogen species, previously ignored, may hold the key to solving this problem. As pointed out by Butcher, these species are fairly mobile and migrate to sample surfaces. “They seem to fit the bill as a culprit for this phenomenon.”
Meaglow is officially launching a range of nitrogen rich InN wafers for sale exclusively on its website to further research and industry collaborations so that all parties can obtain a stronger understanding of InN, and so that the material can realise its full potential.
HIERDA results, reinforces that very nitrogen rich InN can be grown at low temperature.
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