It's all relative: the "high temperature" is high compared to absolute zero (~77 K higher), but much lower than "room temperature" (which is defined as around 2

It's all relative: the "high temperature" is high compared to absolute zero (~77 K higher), but much lower than "room temperature" (which is defined as around 20° C). And of course these are separate categories, because room temperature is another ~220 K higher than "high temperature" (and also because "high temperature semiconductors" are common by now, whereas "room temperature semiconductors" remain the holy grail).