In this report the degradation characteriscs of GaAs/GaAlAs DH LEDs were investigated.The GaAs/GaAlAs DH wafers were grown by LPE technique

the DH LED used in this study was consisted of four layers. The first

n

-Ga

1-x

Al

x

As (

x

=0.35) buffer layer is 6μm thick. The second active layer

p

-Ga

1-x

Al

x

As (

x

=0.05) is 1 μm thick. The third

p

-Ga

1-x

Al

x

As layer is 1-2 μm thick

and the last contact layer is

p

-GaAs

2 μm thick. The output power is above 1 mW. The output power of the tail fibre (inner diameter 60 μm

NA=0.17) is above 60 μW.The degradation characteristics of the devices were investigated at room temperature with inject current of 100 mA. During ageing dark defects in LEDs were observed with an infrared line scanning.The effect of operation time on the

P/P

0

I-V

characteristics and EL pattern was investigated. The results shown that there are two degradation modes. The slow degradation of the LEDs are due to the dark defects(DSD) grown in the action layer of LEDs.The degradation characteristics of GaAs/GaAlAs and InP/InGaAsP DH LEDs were compared. The result indicated that the degradation mechanism for GaAlAs and InGaAsP DH LEDs is different.