The State Of Blue/Green Laser Diodes

The development of the Zn(Se,Te) graded contact scheme to p-ZnSe is found to be effective in supporting the room-temperature CW operation of blue-green (508 nm) laser diodes with a threshold voltage of about 5 volts. Factors contributing to device degradation are analyzed by electroluminescence and plan-view TEM imaging. Both the nucleation/growth of the extended structural defects and the presence of point defects within the active region are responsible for the observed degradation. The more recent exploratory effort on blue-green surface emitting lasers and deep blue (edge emitting) lasers will be reported. Surface emitting laser operation at room temperature at (lambda) equals 496 nm by pulsed optical injection has been demonstrated in a II-VI separate confinement heterostructure cavity. By increasing the energy gaps of the cladding, waveguiding, and quantum well layers, pulsed operation of a 460-nm edge-emitting laser at room temperature was also demonstrated. Electrically, p-type doping of ZnMgSSe is complicated by an apparent increase in the activation energy caused by a mechanism very much like that of the DX center in n-type III-V alloys. These factors must be addressed for II- VI light emitting devices to reach the deep blue part of the spectrum.