| Searching for better performance with less cost is the guidance for the advancement of modern technology, which is especially true for the development of semiconductor lasers. Because of the simplicity and flexibility in device design and fabrication, ridge stripes requiring no epitaxial regrowth have been the most convenient and economical structures for commercial optoelectronics applications. However, due to the insufficient understanding of lateral carrier diffusion and surface recombination, the performance of ridge-waveguide (RW) laser diodes has not been optimized. In this work, the effects of those lateral carrier losses on the light-current and current-voltage characteristics of RW laser diodes have been carefully examined both experimentally and theoretically. As a result of this new understanding, accurate gain measurement and world-record high-performance RW lasers are demonstrated from InGaAs/GaAs quantum-well structures. In addition, an improved device model including the influences of lateral leakage currents has been set up and proven to be able to predict accurately the temperature-dependent threshold behaviors of RW lasers.; In order to further reduce the threshold currents, it is desirable to eliminate the lateral carrier losses in RW devices. In this work, significant reduction of threshold currents in InGaAs/GaAs quantum-well ridge-waveguide lasers has been achieved by using silicon-induced disordering to provide lateral confinement. Room-temperature threshold currents as low as 0.7 mA for pulsed operation and 0.9 mA for cw operation have been obtained from an uncoated device. In addition, the effects of high-temperature annealing on the various device characteristics, such as the gain curve, internal loss and quantum efficiency, have been carefully investigated.; To improve the device performance even further, one way is to replace the active layer with 2-D or even 3-D quantum-confined structures. Here, we report the design, growth, characterization, and modeling of RW laser diodes with a serpentine superlattice nanowire-array active layer. 2-D carrier confinement has been confirmed by the observed optical gain anisotropy at low temperatures. |
