The use of a rare earth gettering technique for the growth of very pure InAs(Sb) epitaxial lavers of high quantum efficiency and its application for the fabrication of powerful 4.6 mu m LEds operating at room temperature is reported. By introducing the rare earth element Gd or Yb into the liquid phase during LPE growth, it is found that the carrier concentration of InAs(Sb) layers can be effectively reduced to similar to 6 x 10(15) cm(-3), and that the photoluminescence (PL) intensity of such layers can be considerably increased by between 10 and 100 times compared with untreated material. This behaviour is attributed to the gettering of residual impurities and the corresponding reduction of non-radiative recombination centres in the presence of the rare earth. This technique is used to purify the InAs0.89Sb0.11 ternary material in the active region of an InAs0.55Sb0.15 P-0.30/InAs0.89Sb0.11/InAs0.55Sb0.15P0.30 symmetrical double hetero structure LED. A pulsed optical output power in excess of 1 mW at room temperature is measured, making these emitters suitable for use in portable instruments for the environmental monitoring of carbon monoxide at 4.6 mu m.