We present experimental results and discuss dependence of the shape and morphology of the solid-vapor interface on growth rate and temperature distribution in the directional "contactless" crystallization of semiconductor materials from group A2B6 and A4B6, and in the conventional vapor growth of ZnO, SiC and iodine. The tendency to grain selection and growth of high quality single crystals was found to be dependent on constitutional supersaturation, gas dynamics and surface kinetics. The evidence of the three kinds of instability was observed on the surface of the crystallization front in various stages of crystal growth. Diagram based on experimental data, summarizing the dependence of the stability criterion on temperature gradient in the crystal and concentration gradient of crystal components in the vapor is presented and discussed. Surface roughening and evoluition of flat faces at the growth interface is investigated. The way of optimization of the growth system by gradual elimination of the mechanisms deciding on the instability is shown. The novel aspect of this work is presentation of validity of the interaction between temperature field and vapor component concentration field, resulting in more general description of the growth system than simple relation between temperature and supersaturation, investigated in former papers.