The interdiffusion of the P-InP with TiPdAu and Au-Zn at interface has been investigated by Auger electron spectroscopy. The results incidate that Ti -and Pd layer as a diffusion barrier plays and important role. The TiPdAu layer is used as the P-electrode of InGaAsP/InP double heterojunction light emitting diodes. The InGaAsP/InP DH wafers were grown by LPE technique. It consisted of three or four layers. The first layer of n-InP was the buffer layer doped with Sn or Te 5-8μm;the second one was an undoped active layer (1-2μm); the third was confining layer of p-InP doped with Zn (2~3μm)

and the last was Zn doped contact layer

with the plated Au as heat sink. The InGaAsP/InP DH LED's were soldered with In onto Au-plated heat sink. The reliability of devices were investigated at the room temperature

70℃ and 85℃ with and without inject current respectively. The experiment was carried out in air. The I-V characteristics of the devices were measured during the aging test. The dark defect in the LED's were observed with an infrared line scanner.The results show that no change of the I-V characteristics is observed. It indicates that the InGaAsP/InP DH LED's made of the TiPdAu as p-electrode have high reliability. The devices made cf the Au-Zn as p-electrode or deep Zn diffusion are different from the devices made of TiPdAu as p-electrode. In the former the large DSD's are generated in the emitting area during aging.