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NEWS REVIEW


Dow Corning sets new standard for 150 mm SiC wafer crystal quality


DOW CORNING, the supplier of silicon and wide-bandgap semiconductor technology, has announced that it now offers 150mm diameter SiC wafers under its Prime Grade portfolio.


Recently launched to set new standards for 100 mm SiC wafer quality, the portfolio also offers three tiers of manufacturing quality 150mm SiC substrates: Prime Standard, Prime Select and Prime Ultra. Each tier offers increasingly stringent tolerances on critical defect types that adversely impact device performance, such as micropipe density (MPD), threading screw dislocations (TSD) and basal plane dislocations (BPD).


“SiC wide-bandgap power semiconductors have rapidly evolved from a cutting-edge niche into an established technology sector that is increasingly focused on the


manufacturing economies afforded by SiC crystal quality, wafer size and other critical factors,” said Tang Yong Ang, vice president, Compound Semiconductor Solutions, Dow Corning.


“Dow Corning’s decision to expand its Prime Grade portfolio to include 150mm diameter SiC wafers aims to meet this very competitive demand.


As we rapidly scale production of these high-quality wafers, our customers will be able to more confidently pinpoint the SiC substrate that optimizes the performance and cost of their next- generation device design while leveraging the improved economies of scale offered by larger wafer diameters.”


While many SiC wafer manufacturers promise low micropipe densities for their 150mm substrates, Dow Corning is


among the first to specify low tolerances of other defect types, such as TSD and BPD. Such defects reduce device yields, and inhibit the cost efficient manufacture of large-area, next-generation power electronic devices with higher current ratings.


Bendy LEDs and solar cells are one step closer


FLEXIBLE ELECTRONICS and optoelectronics devices are usually made with organic materials. But inorganic compound semiconductors such as GaN would offer better optical, electrical and mechanical properties if it were possible to grow them on flexible substrates.


In a new open access journal APL Materials, a team of Seoul National University (SNU) researchers led by Gyu-Chul Yi describes their work growing GaN micro-rods on graphene to create transferrable LEDs and enable the fabrication of bendable and stretchable devices. The picture below shows the process.


“GaN microstructures and


nanostructures are garnering attention within the research community as light-emitting devices because of their variable-colour light emission and high- density integration properties,” explained Yi.


“When combined with graphene substrates, these microstructures also show excellent tolerance for mechanical


heterostructures and quantum structures, and vertically aligned growth onto underlying substrates,” Yi says.


deformation.” Ultrathin graphene films consist of weakly bonded layers of hexagonally arranged carbon atoms held together by strong covalent bonds. This means graphene can provide the desired flexibility with mechanical strength. Also it’s also chemically and physically stable at temperatures in excess of 1,000 O


C.


To create the actual GaN microstructure LEDs on the graphene substrates, the team uses a catalyst-free MOCVD process they developed back in 2002. “Among the technique’s key criteria, it’s necessary to maintain high crystallinity, control over doping, formation of


10 www.compoundsemiconductor.net October 2014 Copyright Compound Semiconductor


When the team put the bendability and reliability of GaN micro-rod LEDs fabricated on graphene to the test, they found that “the resulting flexible LEDs showed intense electroluminescence and were reliable - there was no significant degradation in optical performance after 1,000 bending cycles,” noted Kunook Chung, the article’s lead author and a graduate student in SNU’s Physics Department.


“By taking advantage of larger-sized graphene films, hybrid heterostructures can be used to fabricate various electronics and optoelectronics devices such as flexible and wearable LED displays for commercial use,” said Yi.


The article, ‘Growth and characterizations of GaN micro-rods on graphene films for flexible light-emitting diodes’ by Kunook Chung et al appeared today in the journal APL Materials.


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