In this report

the degradation characteristics of the InGaAsP/InP DH LED’s has been investigated at room temperature (15-35℃) in atmosphere ambient. Two type slow degradation of A and B was suggested. The characteristics of the output power-current

emission spectrum

thermal resistances and series resistance was observed. Tt is found that no change of these characteristics of the InGaAsP/InP DH LED’s undegoes after 10

4

hours cw operation

except slow degradation for B type the normalized output power value P/P

0

decrease slightly about 10-20% at the beginning ageing test.An electroluminescence pattern was observed by means of infrared TV and germanimum photodiode was used as a detector. It is fcund fcr the slow degradation of A type there is no the EL pattern change after 10

4

hours cw operation

but for B type slow degradation with initial dark structure

there is no distingushing variation during EL pattern experiment after 8×10

3

hours cw operation.We explained the degradation mechanism of the InGaAsP/InP DH LED’s by extendng defect model.