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Substrates & Materials Award


Kyma Technologies PVDNC AlN Templates


150mm GaN HEMT epi wafers on SiC substrates


Last May, IQE launched gallium nitride based; high electron mobility transistor (GaN HEMT) epitaxial wafers on 150mm diameter semi-insulating SiC substrates*. IQE believe that GaN power amplifiers offer superior power capability, efficiency, bandwidth and linearity compared to silicon or GaAs-based technologies. They provide significant benefits in terms of higher performance and lower overall system costs.


GaN-based low-noise amplifiers also exhibit improved robustness, noise figure and dynamic range when compared to incumbent solutions In addition, GaN- based transistors can operate at high temperatures, thus reducing system cost, size and weight. As a result, GaN transistors are now established as a leading new technology for a wide range of defence applications.


The 150mm GaN HEMT epi wafer products also enable cost reduction, production capacity and yield improvement, as well as potential for insertion into a wider range of chip fabrication facilities. To date, commercial market penetration of GaN HEMTs has been limited by the higher cost of epitaxial material grown on 100mm SiC substratesGaN HEMT fabrication using LDMOS (laterally diffused metal oxide semiconductor) process lines has been demonstrated by IQE’s customers and the firm’s 150mm products are compatible with existing LDMOS processing lines that have been made available as a result of the silicon industry’s transition to 200mm technology.


*The substrates are supplied by the WBG Materials subsidiary of II-VI Inc.


PVDNC AlN stands for plasma vapour deposition of nano columns. Kyma deposits nano column AlN on silicon and sapphire substrates to create a great nucleation surface for growth of GaN devices thereupon. Device fabricators realize better (lower defect density) GaN buffer layers earlier in the buffer layer growth process. A lower defect density translates to higher thermal conductivity and presents other benefits depending on the device application. Kyma supplies both materials and equipment for making PVDNC AlN templates, which is growing in importance in supporting GaN on sapphire based LEDs and GaN on Si power electronics.


The most difficult part of growing a GaN device on sapphire or silicon is in the initiation of the buffer layer. Kyma’s PVDNC AlN materials present the ultimate in terms of a great nucleation surface for growing GaN based devices on top of it.


The PVDNC process creates a nanostructured AlN surface which is optimal to nucleate GaN growth on top. The process works on both flat and patterned substrates. PVDNC puts an important nano structure on top of flat or micro structured substrates. PVD was thought to be a low-tech approach to growing crystalline films. However, Kyma’s PVDNC process can create perfect nanowires of GaN. When applied to AlN for GaN device applications, PVDNC produces a unique ensemble of highly oriented, highly perfect, AlN nano columns that together present an optimal surface for GaN nucleation.


Rubicon Technology, Inc Patterned Sapphire Last October Rubicon Technology


March 2014 www.compoundsemiconductor.net 63


Inc., announced the launch of the first commercial line of large diameter patterned sapphire substrates (PSS) in four-inch through eight-inch diameters. This new product line provides LED chip manufacturers with a ready-made source of large diameter PSS to serve the needs of the rapidly growing LED general lighting industry.


Most high-brightness LED manufacturers etch a pattern into the sapphire wafers in order to both improve epitaxial growth and extract more light from each chip. Patterned sapphire substrates have been available for purchase in smaller diameters, but Rubicon is the first to offer highly customizable 6” and 8” PSS. The larger substrates increase chipmakers’ throughput and efficiency.


Rubicon offers fully customizable sub- micron patterning capability with tight dimensional tolerances, within ±0.1 µm. With the edge exclusion zone as small as 1 mm, Rubicon offers LED chip manufacturers more usable area to maximize the number of chips per wafer. Patterning is available in a range of shapes including cone, dome and pyramid, and in a range of orientations.


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