We report on the InAs quantum dots (QDs) laser in the 1.55μm wavelength region grown by gas source molecular-beam epitaxy. The active region of the laser structure consists of fivefold-stacked InAs QD layers embedded in the InGaAsP layer. Ridge waveguide lasers were processed and continuous-wave mode operation was achieved between 20 and 70°C, with characteristic temperature of 69K. High internal quantum efficiency (56%) and low infinite length threshold current density (128A∕cm2 per QD layer) was obtained for the as-cleaved devices at room temperature. The lasing wavelength range between 1.556 and 1.605μm can be covered by varying the laser cavity length.

The properties of gas source molecular beam epitaxy grown wavelength extended (2.4 μm) InGaAs photodetector structures on a linear graded InAlAs buffer with different grading rates have been investigated by means of XRD and PL techniques in conjunction with optical and atomic force microscopy. Results show that full relaxation and favorable optical characteristics of the active layers only occur for the wafers with a mismatch grading rate of about 1.2% μm −1 or lower, whereas moderate morphology and structural quality could be achieved for a mismatch grading rate up to 2.4% μm −1 . A thin GSMBE grown linear graded InAlAs buffer layer of 1.4 μm is sufficient to relax the strain of an InGaAs layer with 1.7% mismatch to the InP substrate and reach a good quality of the wafer. The relaxation mechanisms of the buffer at different grading rates were also discussed.

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