We discuss some problems of molecular beam technology (MBE) technology of planar microcavities based on GaAs, AlGaAs and InGaAs compounds. This technology needs specific methods of in situ control and postgrowth characterization. One of the crucial problems is that of controlling the substrate temperature and the growth rate with very high accuracy. We demonstrate the usefulness of substrate temperature oscillations observed by infrared pyrometry for both the temperature and the growth rate control. For studying the perfection of layers and interfaces the cross-sectional transmission electron microscopy has been used. To optimize the optical characteristics of the microcavities, several experimental methods have been applied. The Bragg reflectors were investigated by optical reflectivity. For selective excitation of a quantum well (QW) in a cavity active layer, the Ti-sapphire tuneable laser have been used. The fine tuning between the QW emission and the cavity Fabry-Perot resonance has been investigated by photolominescence for varying temperature of the sample.