Extremely low threshold (AlGa)As modified multiquantum well heterostructure lasers grown by molecular-beam epitaxy

It is shown that by modifying the layer structures of the conventional multiquantum well (MQW) lasers, extremely low Jth of 250 A/cm2 (averaged value) for broad-area Fabry–Perot diodes of 200×380 μm was obtained. This was achieved as a result of utilizing the beneficial effects of the two-dimensional nature of the confined carriers, the improved injection efficiency of the carriers into the GaAs wells, and an increased optical confinement factor in these modified MQW lasers. It was also determined that for low threshold operation the optimal AlAs composition x in the AlxGA1−xAs barrier layers is about 0.19 when GaAs wells are used and for barrier and well thicknesses ≳30 and 100 Å, respectively.