Abstract: An HVPE reactor arrangement comprises a reaction chamber (1), a gas inlet (2) for introducing process gases to the reaction chamber, a residual gas outlet (3), and a pump (4) for evacuating the residual gases from the reaction chamber via the residual gas outlet, the pump being capable of creating and maintaining in the reaction chamber a pressure less than or equal to about 100 mbar. According to the present invention, the reactor arrangement comprises means (6, 7, V2, V3) for supplying dissolving fluid to the pump for dissolving the possible parasitic deposition of the agents of the residual gases on the pump inner surfaces.