AFAIK you can still only buy diamond diodes outside of secret military stuff, and even those are not at all accessible. Sadly GaN suffers from horrible p-chann

AFAIK you can still only buy diamond diodes outside of secret military stuff, and even those are not at all accessible. Sadly GaN suffers from horrible p-channels (they use resistor/nmos logic as the non-differential logic family for GaN ICs), and SiC from kinda sorta delaminating gate oxide (JFETs are fine though, and vertical ones are very nicely behaved, including a lot of resilience like avalanche resistance (though actual (non-capacitive) current flow through the gate junction has to be limited to prevent damage)). N-type diamond is just difficult, along with diamond itself at a purity approximating "intrinsic"/"none" levels of doping. The issue is that you have to continually etch graphitic carbon during the CVD process, requiring aggressive chemistry.