Degradation Processes in Semiconductor Lasers

Various aspects of the failure mechanisms occurring with injection lasers are reviewed, with emphasis on the physical problems involved. Dislocation-related phenomena are known to dominate the short-term problems, and in general dislocations have to be avoided for longlife devices. Both glide processes, which are in general excitation-stimulated, and climb processes, are important, and are discussed in detail. Surface related problems also occur, and they may have a dominant influence on laser characteristics up to an operating time of say 10 3 -10 4 h, mainly due to the oxide formation of the surface. A special surface related problem is the so-called catastrophic degradation at high power levels of pulsed lasers, which is due to thermal runaway and melting at the mirror surface. The long term uniform degradation mode finally, involves recombination enhanced creation and transport of unidentified point defects within the active region of the device, resulting in a gradual reduction of the bulk radiative efficiency and consequently a raise in lasing threshold of a device.