Enhanced performance of an InGaAs/GaAs single quantum well laser diode by introducing a high Al-content Al_xGa_1-xAs cladding layer

We have investigated the effects of an Al_xGa_1-xAs cladding layer on the performance of In_0.2Ga_0.8As/GaAs single quantum well (SQW) laser diodes (LDs). Two types of SQW-LDs with different cladding layers are grown by molecular beam epitaxy. One has 1-mm-thick Al_0.3Ga_0.3As cladding layers for both the top and the bottom cladding layers and the other has 1-mm-thick Al _0.7Ga_0.3As cladding layers. The SQW-LDs are fabricated to a ridge waveguide structure with a 50-mm-wide, 750-mm-long cavity. Under a pulsed operation, the threshold current density (J_th) and the characteristic temperature (T₀) are 770 A/cm² and 33.5 K for a SQW-LD with Al_0.3Ga_0.7As cladding and 300 A/cm ² and 70 K for one with Al_0.7Ga_0.3As cladding, respectively, at room-temperature (RT). This result can be explained by the increased optical confinement and the improved carrier confinement caused by introducing a high Al content into Al_xGa_1-xAs cladding layer.