Infra red TX diode modes of failure

[Marke]

Hi

We use large volumes of infra red TX diodes and have observed a mode of failure and wonder if anyone can shed light on it's cause.

We pulse the LEDs with 600mA current for aout 100uS and a repetition rate of 60mS. The manufacturer agrees that these are within specifications.

We find a small percentage that quickly fail into a "power limiting" mode. i.e. the output power increases linearly from zero current up to around 100mA and then limits at this value for increasing currents. At 600mA it is putting out about the same power as at 75 - 100mA

Any clues as the the mechanism and possible causes of this failure would be much appreciated.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[IRstuff]

Have you tried a curve tracer?

Sounds like the diodes are essentially shorted. I'm surprised that the manufacturer thinks that a 600mA pulse is within specifications. Most semiconductors are prone to failure if the current density increases significantly. High current densities causes the metallization to migrate into the junction causing local shorts.

TTFN