Low threshold 1.5 mu m quaternary quantum well lasers grown by MOCVD

Long-wavelength lasers containing quantum wells (QWs) with compressive strain in the range of 0-1.8% have been grown by atmospheric pressure MOCVD (metal-organic chemical vapor deposition). An ultralow threshold current density of 140 A/cm/sup 2/ at a cavity length of 3.5 mm and very low internal losses of 3.5/cm have been measured for single InGaAsP ( epsilon =1.8%) QW structures. Four QW structures employing quaternary QWs with 0.9% compressive strain exhibited a threshold current density of 324 A/cm/sup 2/ at a cavity length of 1.5 mm. Improvements in low-threshold operation with respect to devices containing strained InGaAs QWs are achieved due to the application of wider quaternary QWs than obtainable for InGaAs with a comparable value of strain. Strained QW lasers exhibited higher modal gain than lattice-matched QW lasers. Double QW structures with lattice-matched wells have operated with a threshold current density of 313 A/cm/sup 2/.<
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