Influence of growth conditions on microstructure and properties of GaSe crystals

GaSe crystals have been grown from melt. There are several reasons why it is difficult to meet ideal demands for nonlinear optic material, GaSe single crystal. First, these crystals have a tendency towards lamination because of great difference in a and c crystal lattice parameters and very weak Vander der Waals forces in c direction. Next, there is a great difference in saturation vapor pressure of the components, which can cause nonstoichiometry of a melt-grown crystal composition. Another obstacle in the growth of perfect GaSe crystals is dendrite formation caused by instability of the growth front. To overcome this obstacle we used Bridgman technique and have found the temperature and pressure conditions, and growth velocity which provide growth of perfect bulk single crystals of about 100 mm in length and 20 mm in diameter. Sharp Laue patterns and a rocking curve confirm perfect structure of the grown crystals. Electron-probe X-ray microanalysis shows stoichiometric composition of GaSe crystals and X-ray phase analysis reveals presence of single-phased hexagonal structure.