Influence of features of QW InGaAs/(Al)GaAs heterostructures grown by MOCVD on the emission spectrum of single-mode laser diodes

Laser heterostructures with an active layer consisted of two strained InGaAs quantum wells are fabricated by the MOCVD epitaxy method. Single-mode laser diodes with a 3 – 4-μm wide stripe contact are made of the heterostructures and their spectral characteristics are studied. It is found that the spectrum of the diodes consists of two groups of longitudinal modes, which cause the spectral broadening. The power distribution between these groups of modes depends on time, the pump current and the temperature of the active region. It is assumed that such a behavior of the diode spectra is explained by the asymmetry of the composition of the diode active region, which arises due to the segregation of In because of the complicated mechanism of its penetrating in the solid solution during the epitaxial growth. This assumption was confirmed by the study of the active region using a modified Auger spectroscopy method.