B.S.T.J. Briefs: Matching of Optical Modes

loading to red (7(MM) A) electroluminescent junctions. T h e diffusion was done in an evacuated and sealed-off q u a r t z t u b e using as a source 1 a Zn + G a P mixture. T h e efficiency of t h e emission w a s d e t e r m i n e d with an integrating sphere and a photomultiplier with S - l response calibrated in absolute unite, and was found at room temperature to be about 1.0 X 10 3 photons per electron for the best samples. Red electroluminescence in G a P was previously reported to h a v e efficiencies of a b o u t 10~4 (see Ref. 3) and 10"4 - 10 1 (see Kef. 4). If silver contacts are alloyed onto t h e rough side of t h e solution-regrown G a P crystals, green electroluminescence can frequently be observed at the contact area. T h e efficiency of t h e green emission was found to be 4 x 10 a photons (5580 A) a t 300°K observed outside the crystal per recombining electron-hole pair for the best samples. T h i s compares with efficiencies of 3 X 10~* measured by Gershenzon et al.* and efficiencies smaller t h a n 10~4 as indicated by Allen et al. 3 T h e figure shows one of t h e red electroluminescent crystals w i t h a Znd iff used junction photographed in its own electroluminescent light. REFERENCES 1. Wolff, ( ; . . Keck, P. H . , unci Broder, J. D., P h y s . Rev.. 94, 1054, p p . 753-754. 2. F o y , P. W., p r i v a t e c o m m u n i c a t i o n . 3. Allen, J. V. t Moncnuter, M. E. f a n d Starkiewicx, J . , Solid-State E l e c t . , 6, 1963, p p . AS 102. 4. C.ershenzon, M.