Phaethon, who Zeus struck from the Chariot of the Sun.
It was not the son of Apollo, but of Helios whose name was Phaethon.
According to the Greek Mythology, Phaethon, whose name means "shining", was the son of the Sun-God Helios and a mortal woman named Clymene
Phaeton
Phaëton
No: Phaeton is the son of Helios.
Phaëton.
Helios is the son of Hyperion. Hyperion is a Titan and a son of Uranus and Gaia. He is married to his sister Theia and has three children - Helios, Selene and Eos.
Phaeton was a son of Helios. His symbol is the sun, though not as grand as that of Helios.
In Greek mythology, Helios is typically associated with the god Zeus as one of his allies. Helios is also often linked with other gods such as Apollo and Hephaestus. Additionally, some stories depict Helios having allegiances with mortal heroes like Hercules or Perseus.
Hyperion
Phaeton was not a god. He was the son of Clymene and Helios, and was struck down by Zeus with a lightning bolt as he was driving his father's chariot.
If by demigod you mean a mortal who had an immortal for a parent, there was Heracles, son of Zeus; Perseus, son of Zeus; Orpheus, son of the Muse Calliope; Achilles, son of the sea nymph Thetis; Deucalion, son of the Titan Prometheus; Phaethon, son of Helios; Asclepius, son of Apollo; Minos, Sarpedon, and Radamanthus, sons of Zeus; Tantalus, son of Zeus; Helen, daughter of Zeus; and Pollux, son of Zeus.