Indium Composition Dependent Threshold Current Density in Strained InGaAs/AlGaAs Quantum Well Lasers

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Abstract
The dependence of threshold current density on indium composition in strained InGaAs/AlGaAs quantum well lasers is examined. A threshold current density (J th) as low as 115 A/cm2 is obtained in a chip with a 500 µm long cavity at a lasing wavelength of 950 nm. The J th for a strained InGaAs QW was found to be 35% less than that for a GaAs QW laser with the same cavity length. Time resolved photoluminescence measurement revealed that the improvement in the nonradiative carrier lifetime for quantum wells with higher indium composition was limited to a J th improvement of only 10%. Calculation suggests that the most likely reason for the major portion of the J th improvement is gain enhancement due to a reduction in heavy hole mass.