Improved performance from pseudomorphic InyGa1-yAs-GaAs MQW lasers with low growth temperature AlxGa1-xAs short-period superlattice cladding

We present results from In sub0.35 Ga sub 0.65 As-GaAs 4 QW lasers whose Al sub0.8 Ga sub0.2 As binary short-period superlattice (SPSL) cladding layers were grown at either 700 degree Celsius or 620 degree Celsius. The threshold current densities (J subth) are about 3 times smaller for the lasers whose AlGaAs cladding layers were grown at 620 degree Celsius. At the same time, the internal differential quantum efficiency (n subi) increases from 6O % to 7O %. We attribute the lower J subth and increased n subi 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. Temperaturedependent 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 subx Ga sub1-x As have achieved 3-dB modulation bandwidths of 24 GHz at record low bias currents of o nly 25 mA.