Embodiments include devices and methods for desorbing molecules from a chamber wall. In an embodiment, a desorption device includes several light emitting diodes (LEDs) mounted on a substrate having a wafer form factor. The LEDs may emit ultraviolet (UV) radiation, such as UV radiation in a UV C range. In an embodiment, the LEDs are thermally coupled to a heat exchanger, such as a thermoelectric cooling device. The emitted radiation may uniformly irradiate a chamber wall to desorb water molecules from the chamber wall. Other embodiments are also described and claimed.