COMPOSITION OF ARSENIC AND PHOSPHORUS VAPOR IN DIFFERENT ANNEALING GEOMETRIES DETERMINED BY RAMAN-SPECTROSCOPY

Furnace annealing of GaAs, InP and related compounds in arsenic and ph osphorus atmosphere, respectively, is carried out usually either in si ngle-zone or in double-zone arrangements. By use of the double-zone fu rnace, the independent control both of the annealing temperature and o f the total pressure is possible. The composition of vapour, i.e. the As-2/As-4 and P-2/P-4 ratio, respectively, depending both on the tempe rature up to 1318 K and on the total pressure (10(-2)-1 bar) was deter mined by Raman spectroscopy analysing the intensity ratio of the vibra tional modes of As-2, As-4 and P-2, P-4, respectively. These experimen tal data were compared with the partial pressure ratio calculated by m eans of the ChemSage database. Raman and ChemSage data show a satisfac tory agreement in case of single-zone experiments. But a systematic de crease of the As-2/As-4-ratio was found in case of the double-zone fur nace. This decrease is attributed to the As-4 how from the source (T-s ) to the optical zone (T-a) depending on the temperature difference (T -a-T-s). The Raman mode of P-2 at 775 cm(-1) was shown for the first t ime. (C) 1998 Elsevier Science B.V. All rights reserved.