Low threshold-current density in 5-layer-heterostructure (GaAl)As/GaAs localised-gain-region injection lasers

Injection lasers have been constructed in which an active GaAs layer is sandwiched between a pair of (GaAl)As layers for carrier confinement and an outer pair of (GaAl)As layers of higher AlAs content for optical confinement. The minimum threshold-current density measured at 300 K. is 575±15 A/cm2 for 0.5 mm-long devices and 390 A/cm2 for lasers with four reflecting faces.