RESEARCH OF STACKED TWIN-ACTIVE LAYER GaInAsP/InP DYNAMIC SINGLE MODE LASERS

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1)The novel stacked twin-active layer structure consisted of two laser regions stacked along the vertical direction, which are connected each other through tunnel junction. When we use this structure for dynamic single mode lasers, a grating is integrated in the tunnel junction part corrugating the surface.2)First, we clarified the impurity doping condition to get a low reverse junction voltage for simple GaInAsP/InP tunnel junctions because the low voltage was essential for connecting two lasers. GaInAsP/InP stacked twin-active layer lasers were fabricated by a liquid phase epitaxy controlling the layer thicknesses in designed values, and the growth condition to connect two active layers by the tunnel junction was obtained. The threshold current density was 2.5kA/cm^2 in average, which was comparable with conventional DH lasers without active layer stack.3)Using the Laser wafer, ridge-waveguide lasers with the stripe width of 3mum were fabricated to get the threshold current of 6OmA a … More t 1.5mum in wavelength. Eventually introducing buried heterostructure is essential, so we tried the use of mass- transportation method to fabricate the buried heterostructure laser. But the degradation of tunneling property was observed after the high temperature annealing process. Thus it was confirmed that the embedding by use of high resistive semiconductors was the only method to embed such a multiple active layers structure.4)The laser waveguide of the stacked twin-active layer GaInAsP/InP dynamic single mode laser was analyzed theoretically. The waveguide design for the fundamental transverse mode operation was given and the laser was fabricated by liquid phase epitaxy. After the growth, the depth of grating became shallow in 200-300A^^ﾟ. This is a specific problem for liquid phase epitaxy, so to avert such a grating deformation the use of molecular beam epitaxy is needed. The threshold current density was 3-4KA/cm^2.5)Through the investigation of lasing properties, it was clarified that for the stacked twin-active layer laser, to equate the thickness of upper and lower active layers was important. So the gas-source molecular beam epitaxy (MBE) with a high thickness controllability, was introduced because GaInAsP compounds could be grown though using MBE. The fundamental growth condition of phosphide compounds such as GaInP and so on was obtained. Less