Laser diodes with the multilayer heterostructure have been observed in
cathodoluminescence (CL) images using an analytical color fluorescenc
e electron microscope. An AlGaInP/GaInP chip, which is commercially av
ailable as 670nm red laser diode, emits red CL from a part of the p-Al
GaInP layer just above the p-GaInP layer and between the n-GaAs blocki
ng layers. A chip that has no blocking layers emits only very weak red
CL, which indicates the strong relation of CL with laser emission. In
images of a CdZnSe/ZnSe diode that emits 5 30 nm blue laser light at
room temperature, a blue CL emission appears which is much stronger in
the n-type region, in particular in the n-ZnSSe cladding layer, than
in the p-type region. Fade-out of the blue CL and/or appearance of yel
low-red emission take place in the area including dislocations.