Quantitative evaluation of gain and losses in quaternary lasers

An excellent quantitative description of the temperature dependence of the laser threshold current density and of the relevant T
o
value of GaInAsP/InP 1.3 μm lasers has been reached by independent measurements of the recombination coefficients and free carrier absorption losses. The recombination coefficients for the radiative band-to-band transition, nonradiative Auger recombination, and extrinsic recombination were determined experimentally, together with the free carrier absorption, especially the contribution of intervalence band absorption. The quantitative evaluation shows that nonradiative Auger carrier losses play the dominant role in the T
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values around room temperature, followed by a smaller contribution due to the intervalence band absorption. Furthermore, combined pressure experiments of laser threshold current and quantum efficiency permit a detailed study of the various loss contributions and demonstrate the influence of the split-off valence band.