Effect of barrier width on the performance of compressively strained InGaAs/InGaAsP MQW lasers

Strained-layer (SL) Multiple Quantum Well (MQW) InGaAs(P)/InGaAsP and InGaAs/InP structures are of large interest for a variety of optoelectronic devices in the 1300 and 1550 nm wavelength regions. Among these devices are lasers, amplifiers as well as modulators based on electrorefraction or electro-absorption effects. Recently, promising results were reported for electro-absorption modulators employing the Wannier-Stark effect. Such modulators need rather thin barrier layers (thickness, ⩽7.5 nm) in order to achieve the required strong coupling between the quantum wells. A powerful technique for monolithic integration of modulators with lasers, waveguides, tapers etc. is area selective growth of MQW structures via Organometallic Vapour Phase Epitaxy (OMVPE). This technique allows local bandgap control and thereby the fabrication of all desired waveguide and active layers in a single epitaxial step. A prerequisite for applying this technique will be that the optimum overall designs (e.g. ratio of barrier to well thickness, confinement layers) of the MQW structures for the various parts are more or less similar. As there is no information available on the barrier thickness-effect on the performance of strained-layer InGaAs/InGaAsP MQW lasers, it was decided to study this for the entire range from coupled to decoupled QWs corresponding to barrier thicknesses from 2.5 to 20 nm