IMPROVED PERFORMANCE FROM PSEUDOMORPHIC INYGA1-YAS-GAAS MQW LASERS WITH LOW GROWTH TEMPERATURE ALXGA1-XAS SHORT-PERIOD SUPERLATTICE CLADDING

We present results from In0.35Ga0.65As-GaAs 4 QW lasers whose Al0.8Ga0.2As binary short-period superlattice (SPSL) cladding layers were grown at either 700 degrees C or 620 degrees C. The threshold current densities (J(th)) are similar to 3 times smaller for the lasers whose AlGaAs cladding layers were grown at 620 degrees C. At the same time, the internal differential quantum efficiency (eta(i)) increases from 60% to 70%. We attribute the lower J(th) and increased eta(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 AlxGa1-xAs have achieved 3-dB modulation bandwidths of 24 GHz at record low bias currents of only 25 mA.