INFLUENCE OF THE ATMOSPHERE DURING HEAT-TREATMENT ON THE FORMATION OF DEEP-LEVEL CENTERS

An investigation was made of the influence of various factors on the spectrum of deep-level centers formed as a result of heat treatment of n-type silicon. Annealing in an argon stream or in vacuum generated three deep-level centers with the ionization energies E3 = E(c) - 0.455, E5 = E(c) - 0.266, and E7 = E(c) - 0.193 eV and with the electron-capture cross sections sigma-3 = 1.2 X 10(-14), sigma-5 = 4.0 X 10(-16), and sigma-7 = 5.1 X 10(-16) cm2. Vacancies played the dominant role in the formation of these centers. Heat treatment in an oxidizing medium (dry oxygen and an atmosphere containing chlorine) resulted in predominance of two deep-level centers with E1 = E(c) - 0.535 and E4 = E(c) - 0.277 eV and sigma-1 = 1.6 X 10(-15) and sigma-4 = 1.9 X 10(-17) cm2, which were formed as a result of supersaturation of silicon with interstitial host atoms. The diffusion of aluminum and boron in an argon stream or in vacuum resulted in the formation of the E4 center and in an oxidizing atmosphere it could be accompanied by the formation of the E7 and E8 centers (E8 = E(c) - 0.185 eV, sigma-8 = 4.0 X 10(-14) cm2). The E8 centers were formed because of enrichment of silicon with oxygen. An analysis was made of the factors responsible for the very large differences between the parameters of the deep-level centers, formed as a result of heat treatment of silicon, which were reported by different authors.