Investigation of rare earth gettering for the fabrication of improved mid-infrared LEDs

The use of a rare earth gettering technique for the growth of very pure InA s(Sb) epitaxial lavers of high quantum efficiency and its application for t he fabrication of powerful 4.6 mu m LEds operating at room temperature is r eported. By introducing the rare earth element Gd or Yb into the liquid pha se 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 th at the photoluminescence (PL) intensity of such layers can be considerably increased by between 10 and 100 times compared with untreated material. Thi s behaviour is attributed to the gettering of residual impurities and the c orresponding reduction of non-radiative recombination centres in the presen ce of the rare earth. This technique is used to purify the InAs0.89Sb0.11 t ernary material in the active region of an InAs0.55Sb0.15 P-0.30/InAs0.89Sb 0.11/InAs0.55Sb0.15P0.30 symmetrical double hetero structure LED. A pulsed optical output power in excess of 1 mW at room temperature is measured, mak ing these emitters suitable for use in portable instruments for the environ mental monitoring of carbon monoxide at 4.6 mu m.