Optical Properties of full digital-alloy InGaAlAs Multi-quantum wells and Application to CW 200-mW 1.3-/spl mu/m Laser Diodes

We report optical properties of full digital-alloy InGaAlAs mutli-quantum wells (MQWs). All layer of InGaAlAs consist of short period superlattices of sub nanometer thick InAlAs and InGaAs. We found that the activation energies of the MQWs are closely related to pits of electron reflections in digital-alloy InGaAlAs. Finally, we report 200 mW CW operation of 1.3 μm full digital-alloy InGaAlAs laser diodes. nGaAlAs/InP has received considerable attention as an important alternative system to conventional InGaAsP/InP for the application of 1.3 - 1.55 μm uncooled laser diode and surface-emitting laser diode,(1) because the former has a higher characteristic temperature (T0) due to a larger conduction band offset,(2) and a larger refractive index difference.(3) Molecular beam epitaxy (MBE) is promising growth technology considering the benefits of the ultra-vacuum environment such as low incorporation of oxygen impurity during the growth of aluminum-containing material and availability of ultra-high-purity aluminum source. Additionally, the conventional problem with the growth of phosphides by MBE has been almost solved by many approaches.(4) However, in order to obtain multiple-alloy In1-x-yGayAlxAs, rigorous attentions should be paid on the growth interruption and change of source cell temperature, or additional source cells must be equipped to conventional MBE system. Digital-alloys, or short-period superlattices (SPSs) consisting of binary or ternary layers with a period of a few monolayers (MLs), has emerged not only as a solution for the growth of ternary or quaternary materials of various composition without additional source cells and laborious change of cell temperature during