High-power Al-free InGaAsP/GaAs near-infrared semiconductor lasers

We have developed low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technology for the growth of Al-free In_xGa_1-xAs_1-yP_y compounds lattice-matched to GaAs substrate for the emission wavelengths of 0.808 and 980 nm. The measured device characteristics such as threshold current density J_th, differential efficiency η_d and characteristic temperature T₀, optical loss α_i are compared with model calculations. From these comparisons, it is shown that the Al-free InGaAsP systems have almost 100% internal efficiency, having no significant non-radiative recombination recombination that can affect laser operation. It is shown, however, that the lasers, particularly, optical loss and gain spectrum are rather strongly affected by the material alloy composition fluctuation in InGaAsP active region. The laser structure and fabrication were optimized based on these results for highly efficient high temperature high power laser operation. Maximum output powers up to 7 W in CW and 8 W in pulse were obtained from the 0.808-μm InGaAsP/GaAs lasers with the optimized structure. Lifetime testing shows no degradation in laser performance for over 30,000 hours in any of randomly selected several 100 μm-wide uncoated lasers operated at 60°C with 1 W continuous wave output power.