LEDs for application in long-haul optical communication system are characterized by their high effective radiance and the long-term reliability.Although diodes having hemispheric or spheric lens on the emitting surface exhibit higher external efficiencies

but such devices are too expensive to make for this application purpose.Therefore in the present work

we investigated the effect of front facet sputtered A1

2

O

3

coating on light output increase of In GaAsP-InP LED.A conventional RF sputtering equipment with the source power 3kW at 13.5MC was used in deposition of A1

2

O

3

AR coating.A high purity A1

2

O

3

disk was employed

as target.The calulated results show that reflectivity of A1

2

O

3

AR coating on InP surface is very low.It’s coefficient of thermal expansion (α=6.8×10

-6

℃

-1

) is approximately comparable to that of In P (α=4.5×10

-8

℃

-1

).In order to eliminate possible second electrons bombardment on devices during deposition of A1

2

O

3

coating.It is necessary to modify the sputtering equipment to provide a “region without damage” on the surface of the substrate table where diodes are placed for A1

2

O

3

coating.