news digest ♦ Power Electronics
contract marks the beginning of a technological leap in device performance and efficiency for power semiconductors. The development will enable a significant step toward producing 20 kV AlN-based Schottky diodes (SBD, JBSD) and transistors (JFET, MOSFET). The ARPA-E contract has opened the door for the material development and research to demonstrate AlN high-voltage, high- efficiency power conversion capability.”
For power systems and grid-scale power conversion applications, high efficiency AlN-based power devices will offer a significant reduction in size, weight, and cooling. Power semiconductor devices at this level are not currently available on the market. Experimental devices based on SiC technology are currently being developed. Compared to SiC technology, it is expected that AlN will enable power electronics with a ten times improvement in performance.
Based on the wide bandgap material properties of AlN, the critical field is six times larger, the on resistance will be lower, and the resulting power device area will be smaller for a comparable power level. This is a transformational technology that will revolutionise the power distribution grid.
Controlling GaN-on- silicon(001) growth with insitu monitoring
Laytec has reported EpiCurve TT results obtained during the growth of gallium nitride HEMTs on Si(001) substrates
The growth of GaN on Si(111), especially for LEDs, is quite well known and relatively controllable.
Cooldown-assisted layer cracking as a result of high tensile stress can be prevented and crystal quality can be enhanced by sophisticated interlayers. Many institutions are using LayTec‘s EpiCurve TT tool with advanced curvature resolution to grow high quality GaN devices on large scale (111) silicon substrates.
Now, this experience is being transferred to growth on Si(001) and Si(110) substrates. This is because GaN based power electronics can be easily integrated with standard silicon electronics (CMOS).
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www.compoundsemiconductor.net January/February 2013
Figure 1: In-situ measurements of temperature (red) and curvature (black)by EpiCurve TT during GaN on Si(001) growth.
The three combined reflectance signals help to determine the growth rates and allow adjustment of the growth parameters. In addition, the 405 nm reflectance (the black line in Figure 2 below), provides information on the structural interface quality.
What’s more, like Si(111), these substrates are also available in large sizes of up to 300 mm.
In October 2012, Jonas Hennig of Otto-von- Guericke Universität Magdeburg in Germany reported results on high performance GaN HEMT structures grown on Si(001). The structures incorporated highly optimised interlayers to control stress and defect density.
The results were presented at the International Workshop on Nitride Semiconductors in Japan.
According to Hennig, in-situ growth monitoring by Epi-Curve TT is a great help for their strain engineering.
The well pronounced Fabry-Perot oscillations at 633 nm (red) and 950 nm (blue) in correlation with the smooth development of the curvature show the high quality of the GaN. What›s more, during the growth of interlayers, when the temperature is being reduced, an abrubt increase in curvature can be observed as shown in Figure 1 below.
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