A desert was a dry area of a planet that had very few sources of water. (TV: The Chase) Desert terrain often consisted only of sand and stone. (AUDIO: Last of the Colophon) There were whole planets that were deserts, called desert planets, including Aridius (TV: The Chase) and San Helios after it was ravaged by the Swarm. (TV: Planet of the Dead)
Sontar sand shrews inhabited the deserts on Sontar. (PROSE: The Sontaran Games)
Gethria was a largely desert planet. (PROSE: The Dalek Generation)
In the New Sahara timeline, Earth's surface was turned to desert by the Krykkani. (PROSE: Red Rover Red Rover)