It's been eons since I touched this stuff, but the article said that they're on GaAs on Si wafers for a substrate. Is that the usual these days? ISTR that SiC

It's been eons since I touched this stuff, but the article said that they're on GaAs on Si wafers for a substrate. Is that the usual these days? ISTR that SiC was always a PITA to grow on decent/cheap substrates, which may have held it back. That and it didn't have the whole blue LED industry driving it.