The threshold current and the wavelength of a high-power ridge waveguide AlGaAs graded index seperate confinement heterostructure quantum well laser have been studied in strong magnetic fields up to 20 T, to simulate the complete quantum confinement of carriers in a quantum box laser. It will be shown both experimentally and theoretically that the threshold current is increased by the application of a strong magnetic field, while its temperature sensitivity is reduced. It will further be shown that at low temperatures (T<100 K) laser emission occurs via both free carrier and excitonic transitions, while at higher temperatures (T>100 K) exciton laser emission is only observed after application of a strong magnetic field, i.e., reduction of the dimensionality.

GaAs/AlGaAs quantum wells (QWs) were grown by molecular beam epitaxy on GaAs (100) substrates patterned with ridges and grooves in the [011̄] direction. Low-temperature cathodoluminescence was used to measure the Al fraction and QW thickness on top of the ridges and grooves as a function of ridge and groove width. Surface diffusion during growth depletes Ga from the side facets while increasing the incorporation of Ga on the (100) sections of ridges and grooves. The QW thickness on top of a ridge grown at 710 °C increases from 72 to 95 Å, and the Al fraction x decreases from x=0.33 to x=0.29 as the ridge width is narrowed from 30 to 4 μm. Graded refractive index separate confinement heterostructure lasers with nominally 70 Å QWs and Al0.2Ga0.8As barriers were grown on patterned substrates at 695 and 725 °C. Lasers fabricated on the overgrown 4-μm-wide ridges have a 20 meV decrease in emission energy compared to laser diodes on 30 μm ridges.

An undercut mesa laser is fabricated on an n+-InP substrate using a single step liquid phase epitaxy growth process and a planar structure is obtained by using a polyimide filling layer. The lasers operate at fundamental transverse mode due to a scattering loss mechanism. Threshold currents of 18 mA and stable single transverse mode operating at high currents are obtained.

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We present results of a comparative study of the time-dependent luminescence properties of multiple quantum well structures with varying barrier widths which are embedded in the active area of a light-emitting device. The carrier kinetics is investigated by different experimental approaches: Cathodoluminescence and electroluminescence experiments where excitation is on/off-modulated for the purpose of time-resolved measurements and time-resolved electroluminescence experiments in the small signal regime which allow for observation of the carrier kinetics under flatband conditions. Due to the exact determination of the excess carrier density the latter technique provides a sensitive tool for a precise estimation of the mono- and bimolecular recombination coefficients. Comparison with light output data yields radiative and nonradiative parts. We find that coupling of quantum wells dramatically favors nonradiative interface recombination as expected from a theoretical model accounting for the superlattice wavefunctions. On the other hand, the bimolecular recombination rate remains unaltered even when the barrier width is lowered from 18 to 0.9 nm. In contrast, on/off modulated experiments reveal that luminescence decay is strongly influenced by carrier drift out of the active area. A barrier width dependent carrier mobility in growth direction accounts for these results if phonon assisted hopping rather than Bloch transport is presumed. Thus, an estimation of device quality of quantum well light emitters by conventional time-resolved cathodo- (or photo-) luminescence experiments is found to be possible if internal field induced carrier drift processes are taken into account.