| In conventional quantum well lasers, carriers are injected over the hetero-barrier into the quantum wells with quite high energies. If carriers do not thermalize as fast as they are depleted by stimulated emission, the carrier distribution will become hot, causing gain compression at high optical powers. In order to overcome the intrinsic limitations in present semiconductor laser design, a new device concept--the tunneling injection laser--has been investigated. In the tunneling injection laser, electrons are injected into the active quantum well by tunneling instead of thermalizing over the quantum well barrier. The tunneling injection lasers are shown to have negligible gain compression, superior high temperature performance, lower Auger recombination and wavelength chirp, and better modulation characteristics when compared to conventional lasers. The underlying physical principles behind the superior performance are discussed.; Design, fabrication, and characterization of high-speed lasers are investigated. To achieve the highest bandwidth, optimizations for differential gain and carrier transport are crucial. We utilize strain-compensated InGaAsP quantum well structures for the active layer and fabricate ridge waveguide and buried heterostructure lasers. High modulation bandwidths of 23-24 GHz are demonstrated for these lasers. Carrier dynamics in gain-switched lasers has been investigated for application to a multi-laser-multiplexed optical transmitter.; The effect of the strain in the quantum well on the reliability of multiple quantum well lasers is investigated. An improvement in the reliability of these devices with increased strain in the wells is observed. The impediment of point defect migration into the active region due to the strained quantum wells is the dominant mechanism for this improvement. The mechanism has been confirmed by performing accelerated lifetime tests of lasers and photoluminescence measurements on specially designed heterostructures. A theoretical model, based on the propagation of point defects, explains these results. |
