In-plane photoluminescence of vertical cavity surface-emitting laser structures

Vertical cavity surface-emitting lasers (VCSELs) are only effectively lasing, when the emission wavelength of the quantum well (QW) coincides with the Fabry-Perot resonances of the inner cavity and with the maximum reflectivity wavelength of the Bragg reflectors. In order to characterise epitaxial structures before laser processing a method for the rapid determination of quantum well emission and thicknesses of lambda/4-layers in the mirror is developed. The in-plane photoluminescence spectrum of a complete VCSEL structure is measured at room temperature by optical excitation perpendicular to the sample surface. Since the PL spectrum consists of the QW luminescence and additional features originating from interferences in the Bragg reflector the thicknesses of the mirror layers can be determined.