We report molecular beam epitaxy (MBE) growth and device performance of 1.3μ m GaInNAs/GaNAs singlequantum well lasers on GaAs substrates. Record low threshold current densities of 300, 320 and 360A/cm(2) for cavity lengths of 1200, 1000 and 800 μ m, respectively, and a transparency current density of only 84 A/cm(2) are achieved for the 100 put wide broad area lasers. A characteristic temperature of 108 K is measured in the temperature range of 8-70 ° C for a laser with a cavity length of 1000 μ m. We find that optimization of the RF nitrogen source during the MBE growth plays a crucial role in reducing the threshold current density. © 2005 Elsevier B.V. All rights reserved.