Tensimetric Studies of Arsenic and Phosphor Vapor Composition

Main active elements in the frequency range from a few to a hundred gigahertz still are field-effect transistors with Schottky barrier based on gallium arsenide, other AB compounds and various heterostructures based on them. For optoelectronics, gallium phosphide and its compounds are of high importance. As a rule, these heterostructures are obtained by vapor phase methods, the use of which requires correct data on volatile components vapor composition. In this work, arsenic and phosphor vapor composition was studied by tensimetric static method. A mathematical model for processing of experimental results was built. Data on superheated arsenic vapor pressure were obtained using quartz gauge membrane in the range of temperature 973-1173 K and pressure 1,3∙10-1,9∙10 Pa. The calculations have found that arsenic and phosphor vapor mainly consist of two- and four-atomic molecules. Using best documented reference data on As, As, P and P enthalpies and entropies, corresponding thermodynamic values have been determined for As: = (178,90 ± 3,77) kJ/mol, = (227,17 ± 5,44) J/(mol·K); and for P: = (229,01 ± 3,55) kJ/mol, = (156,16 ± 0,83) J/(mol·K).
Evgeny N. Vigdorovich
MIREA – Russian Technological University, Moscow, Russia