Tuesday, December 02, 2008

18 Hours of Photo-Luminescence (PL) Mapping

Seems like I miscalculated the time for PL mapping of my LD sample. Did many times PL mapping for blue-violet LED samples before, normally it takes around 4 hours to map a 2 inch wafer.

This time, it is a LD sample. When I tested it this morning, the light intensity from the surface is very low, probably due to the LD structure itself which holds light within the active layer region (prevents light from being leaked to the surface). Therefore, I need to increase the detector scanning time to 3 sec (normally 0.2 sec) for each scan. There're 97 times scan of the circle 2" wafer surface with 0.5 mm pitch between each other. The stage controller also needs a few seconds to move the He-Cd laser to each pitch position, and the workstation also becomes slower and slower with increasing scan times... altogether causing an extremely slow experiments!

Normally, I could finish 2 samples in a day for normal LED samples, but for this LD sample, it takes my 2 days working hours just to finish a single sample. It's already 1:15AM in the midnight, I wonder where I would sleep tonight...

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