EXCELLENT UNIFORMITY AND VERY LOW (LESS-THAN-50 A/CM2) THRESHOLD CURRENT-DENSITY STRAINED INGAAS QUANTUM-WELL DIODE-LASERS ON GAAS SUBSTRATE

We report the growth and fabrication of InGaAs/GaAs strained quantum well (QW) lasers with a very low threshold current density, J(th), of < 50 A cm-2 emitting at 0.98-mu-m. The lasers, 1350-mu-m long, had two InGaAs 80 angstrom quantum wells in the active region and Al0.6Ga0.4As in cladding layers, and were grown on 3-degrees off (100) towards <111>A GaAs substrate. Misorienting the substrate towards <111>A improves the material quality and device performance substantially for x almost-equal-to 0.6 in the cladding layer, but degrades it somewhat for x almost-equal-to 0.35. The J(th) 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 X 1016-mu-m size bar, representative of the whole 5-cm-diam substrate, exhibited a yield of > 90% and an excellent spatial uniformity of J(th) and emission wavelengths which were 212 +/- 4 A cm-2 and 989 +/- 1 nm, respectively.