> Or use the (imperfect) GaN crystals to grow incrementally better crystals over multiple rounds?
This is exactly what's often done. It's all about scale fundamentally. It's slow to grow crystals, they have to be very high quality single crystals, and they can't have even the slightest trace of impurities, and ideally they're going to be large and easy to process too. If an alternative substrate is also hard to grow at scale, it's not going to work. But I don't want it make it sound like it's just a scaling issue, because to my knowledge better substrates haven't been found even as a proof of concept. It's not just lattice parameters, but a whole host of other things too. But people are still looking :)
> People have tried zeolites in the past, but surprisingly a random speck of dust sometimes works better than the best designed substrate.
Hah, that sounds both incredibly frustrating and good fun!
Not specifically. I haven't really heard it mentioned, but I don't actually do growth myself. It's mostly Stranski-Krastanov growth with islands growing until they coalesce. There's not really any significant flow of atoms between islands to my knowledge. What's your interest in it?
One of my labmates from grad school did colloidal quantum dot synthesis, and he regularly cursed Ostwald and his infernal ripening. Just general curiosity if it came up in this area, and if so, how it was dealt with.
By the way, your series of posts on this topic have been superlative—many thanks.
This is exactly what's often done. It's all about scale fundamentally. It's slow to grow crystals, they have to be very high quality single crystals, and they can't have even the slightest trace of impurities, and ideally they're going to be large and easy to process too. If an alternative substrate is also hard to grow at scale, it's not going to work. But I don't want it make it sound like it's just a scaling issue, because to my knowledge better substrates haven't been found even as a proof of concept. It's not just lattice parameters, but a whole host of other things too. But people are still looking :)
> People have tried zeolites in the past, but surprisingly a random speck of dust sometimes works better than the best designed substrate.
Hah, that sounds both incredibly frustrating and good fun!