Electrically pumped, surface-emitting distributed feedback lasers were for the first time demonstrated without any facet reflections. The devices contained second-order gratings etched into a thin p-AlGaAs cladding layer surface. A gold ohmic contact deposited directly onto the p-AlGaAs grating surface provided strong coupling to the waveguide mode. Single spatial mode devices with low divergence output beams and single frequency spectra were obtained at room temperature.
Monolithic two-dimensional arrays with light emission normal to the surface have been obtained by fabricating edge-emitting quantum well GaAs/AlGaAs lasers with deflecting mirrors adjacent to both laser facets. The facets and mirrors were formed by ion beam assisted etching. Proton bombardment between adjoining lasers was used to prevent lasing in the transverse direction. At the highest pulsed current used in these experiments, 10.5 A, the power output of a 22-element array was 1.6 W, which corresponds to a power density of 160 W cm−2. At this level, the power output was still linear with current.
We report photoreflectance studies ofMOCVD grown doped GaAs at the higher energy transition E1( 2.9 eV). We are especially interested in the variation ofboth the energy position and the broadening parameter F of the E1 transition with doping concentration. Above 1 x 10'8cin3 for Si:GaAs and ' 7 X 1018 for Zn:GaAs, we observe an increasing overlap of B1 and E1 + Li structures. Evaluation of r based on curve fitting of the KramersKronig analysed data shows a nearly linear relation between F and the logarithm of carrier concentration. This observation has potential application in the determination of carrier concentration for heavily doped films.
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