Analytical color fluorescence electron microscopy observation of laser diodes

Laser diodes with the multilayer heterostructure have been observed in cathodoluminescence (CL) images using an analytical color fluorescence electron microscope. An AlGalnP/GalnP chip, which is commercially available as 670 run red laser diode, emits red CL from a part of the p-AlGalnP layer just above the p-GalnP layer and between the n-GaAs blocking 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 530 run 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 yellow-red emission take place in the area including dislocations.