Book excerpt: This book presents a new and promising technique to grow single crystalline compound semiconductor materials with defined stoichometry. The technique is based on the high-precision experimental determination of the boundaries of the single-phase volume of the solid in the pressure-temperature-composition P-T-X phase space. Alongside test results obtained by the author and his colleagues, the P-T-X diagrams of other important materials (e.g., III-V, V-VI semiconductors) are also discussed.