Improved performance from pseudomorphic InyGa/sub 1-y/As-GaAs MQW lasers with low growth temperature AlxGa/sub 1-x/As short-period superlattice cladding

We present results from In/sub 0.35/Ca/sub 0.65/As-GaAs 4 QW lasers whose Al/sub 0.8/Ga/sub 0.2/As binary short-period superlattice (SPSL) cladding layers were grown at either 700/spl deg/C or 620/spl deg/C. The threshold current densities (J/sub th/) are /spl sim/3 times smaller for the lasers whose AlGaAs cladding layers were grown at 620/spl deg/C. At the same time, the internal differential quantum efficiency (/spl eta//sub i/) increases from 60% to 70%. We attribute the lower J/sub th/ and increased /spl eta//sub i/ to a significant decrease in the concentration of point defects in the MQW active region, consistent with the observed improvement of the diode ideality factor. Temperature-dependent photoluminescence (PL) results suggest that these nonradiative recombination centers are related to point defects recently observed with Raman scattering. Ridge lasers grown with low-temperature SPSL Al/sub x/Ga/sub 1-x/As have achieved 3-dB modulation bandwidths of 24 GHz at record low bias currents of only 25 mA.<
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