Strained and partially relaxed In1-xGa xAs yP1-y /InP single quantum wells (SQWs) with different cap layer thicknesses and biaxial strain values grown by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) were investigated by double crystal X-ray diffraction, photoluminescence microscopy (PLM) imaging and photoluminescence spectroscopy techniques. Our results indicate a significant improvement of the optical quality of the quaternary wells with increasing values of the cap layer thickness. Tensile and compressive strained In1-xGa xAs yP1-y /InP SQWs grown with the same structure exhibited different relaxation processes, even when the strain magnitude was the same. PLM images of highly compressive quantum wells exhibited a large number of dark lines corresponding to misfit dislocations as a result of the partial relaxation process in the well material. PLM images of similar tensile strained samples revealed only the presence of dark spots with no evidence of misfit dislocations.

The modulation frequency response of compressively strained multiquantum well (MQW) lasers grown with an InGaAs/AlGaInAs/InP heterostructure and emitting at the wavelength of 1.55 <FONT FACE="Symbol">m</font>m is presented. The laser devices processed with the mushroom-stripe buried structure present a high frequency 3 dB bandwidth above 20 GHz. The frequency response was measured with the small signal modulation technique. The logarithmic subtraction method was employed to extract the intrisic frequency response of the MQW active layer, providing the determination of important laser parameters: the differential gain, the nonlinear gain coefficient and the maximum 3 dB frequency bandwidth.

We present measurements of the differential gain of multiquantum well (MQW) broad area lasers emitting at 1.55<FONT FACE="Symbol">m</font>m wavelength, taking into account the nonuniform stimulated emission caused by filamentation within the optical cavity. The differential gain was determined from measurements of the threshold current density, considering the losses due to the inhomogenous carrier density distribution, as an apparent leakage current effect in the output power-current characteristics. The lasers were grown by low pressure MOCVD and incorporate an InGaAs/InGaAsP/InP separate confinement MQW active region. The results are compared with previous data reported on similar MQW heterostructures.