Light emiting transistors?
This won't work. FETs don't conduct current the same way as BJTs (NPNs, PNPs) do. They are majority carrier devices, which basically means that there isn't a current flowing across a PN junction. 

Even if you could, GaAs transistors are not engineered to be efficient light emitters, and wouldn't emit in the visible region. You wouldn't see anything.

PN junctions do emit some photons when carriers are recombining, but the levels are extremely low, and not practical.