Excellent uniformity and very low (<50 A/cm2) threshold current density strained InGaAs quantum well diode lasers on GaAs substrate

Abstract

We report the growth and fabrication of InGaAs/GaAs strained quantum well (QW) lasers with a very low threshold current density, Jth, of <50 A cm−2 emitting at 0.98 μm. The lasers, 1350 μm long, had two InGaAs 80 Å quantum wells in the active region and Al0.6Ga0.4As in cladding layers, and were grown on 3° off (100) towards 〈111〉A GaAs substrate. Misorienting the substrate towards 〈111〉A improves the material quality and device performance substantially for x≊0.6 in the cladding layer, but degrades it somewhat for x≊0.35. The Jth increased about 25% with decreasing x from 0.6 to 0.35 due to decreased optical confinement. Single QW stripe lasers with x=0.35 tested on a 3.0 cm×1016 μm size bar, representative of the whole 5-cm-diam substrate, exhibited a yield of ≳90% and an excellent spatial uniformity of Jth and emission wavelengths which were 212±4 A cm−2 and 989±1 nm, respectively.