High-gain InP-based quantum dot lasers for telecommunication applications

This paper reports on the realization of high gain QD lasers for 1.55 μm optical fiber communication. Using a recently developed growth recipe, InAs/InAlGaAs/InP QD material with reduced inhomogeneous linewidth broadening of less than 30 meV was obtained. All structures are grown by solid-source molecular beam epitaxy (MBE) using valved cracking cells for generation of As₂ and P₂. The achievement of round-shaped quantum dots on InP substrates is more complex than in the InAs/GaAs system, since the lattice-mismatch is only 3.2%. Therefore, anisotropic effects on the growth front are more dominant and typically elongated quantum dashes rather than dots are obtained. By introducing As₂ during the growth of the InAs material the nucleation and growth evolution of the nanostructures can be significantly altered. It is worth noting that all other growth parameters are kept constant. Only the arsenic species was changed from As₄ to As₂.