technology GaN transistors
European efforts propel nitride devices to a new level
The first GaN HEMTs grown on free-standing diamond, GaN pressure sensors with various designs, robust chemical sensors and power amplifiers delivering hundreds of watts are some of the many highlights of the European project entitled MORGaN. The programme’s leader, Sylvain Delage from III-V Lab, details the many accomplishments.
A Ga0.75
tried and tested route for improving device performance involves the introduction of
N/GaN cousin, enabling devices with higher frequency capabilities. And on top of this, it is possible to wring out further improvements by switching to diamond substrates, a step that aids thermal management of the device.
new, superior material combinations. This can pay dividends with nitride electronics, which are traditionally based on the pairing of GaN and AlGaN. The introduction of InAlN in place of AlGaN reduces stress, leading to enhanced output powers and superior high temperature capability. What’s more, thanks to far stronger spontaneous polarization, the InAlN/GaN heterojunction produces twice the charge density of its Al0.25
Another goal of the MORGAN project is to exploit the thermal and physicochemical robustness of diamond. The former target has involved the development of new silicon/polydiamond composite substrates, along with the deposition of a nanocrystalline diamond coating on top of the wafer to enhance heat removal. Diamond coatings can also protect GaN, which is a major asset when this wide bandgap material is used to make sensors operating in aggressive electrochemical solutions.
Advances such as these have just been realized in a three-year project entitled Materials for Robust GaN (MORGaN). This effort, which kicked-off in November 2008 and was backed by €9.2 million (about $13 million) of funding from the European Commission, involves 23 industrial and academic partners from 11 nations (see Figure 1 for details).
The great promise of the GaN/InAlN heterostructure came to light in a forerunner of MORGaN, a project known as UltraGaN, which started in 2005. Thanks to the success of both these projects, the InAlN/GaN heterostructure is now under close investigation by major research laboratories worldwide for its specific advantages in optoelectronic and microelectronic applications.
Figure
1.The European Commission funded project MORGaN – Materials for Robust GaN – involved 23 industrial and academic partners from 11 nations
April / May 2012
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