Very low threshold current density 1.5 μm GaInAs/AlGaInAs graded‐index separate‐confinement‐heterostructure strained quantum well laser diodes grown by organometallic chemical vapor deposition

Very low threshold current densities of 200 and 400 A/cm2 were obtained in 1.5 μm GaInAs/AlGaInAs tensile and compressive strained‐layer quantum well laser diodes (SL‐QW LDs), grown by organometallic chemical vapor deposition, with continuously graded‐index separate‐confinement‐heterostructure. The differential quantum efficiency of SL‐QW LDs showed less sensitive to temperature in contrast to that of a lattice matched QW LD. This is attributed to the decrease of intervalence band absorption due to the strain‐induced reduction in the valence band density of state. The polarization of output power for a tensile SL‐QW LD showed transverse magnetic (TM) mode, while that for a lattice matched and a compressive SL‐QW LDs showed transverse electric (TE) mode.