Strained-layer InGaAs-GaAs-AlGaAs lasers grown by molecular beam epitaxy for high-speed modulation

A study of strained InGaAs quantum wells grown on GaAs by molecular beam epitaxy was performed in order to optimize the growth conditions for strained-layer single- and multiple-quantum-well lasers. Photoluminescence of the quantum wells shows a rapid degradation in material quality as the substrate temperature is reduced below 500°C. Single-quantum-well (SQW) laser structures contain a 55 Å 35% InGaAs quantum well, while multiple-quantum-well (MQW) lasers contain four 25% or 35% InAs mole fraction 55 Å quantum wells. The 35% SQW lasers emit at 1.06 μm, while the 25% InGaAs MQW lasers emit at 1.07 μm. The SQW lasers have threshold current densities as low as 83 A/cm² for 150×1000 μm devices. Microwave modulation bandwidths increase with an increasing In mole fraction and number of quantum wells, as predicted by theory. A differential gain of 5.0×10^-15 cm² is calculated from the microwave response measurements for the 35% MQW devices