INITIAL GROWTH-CHARACTERISTICS OF GERMANIUM ON SILICON IN LPCVD USINGGERMANE GAS

The growth characteristics in the initial stage of Ge epitaxy on the S i(1 0 0) epitaxial buffer layer have been investigated by ultraclean L PCVD at 350 degrees C using GeH4 at 0.2 and 12 Pa with H-2 or Ar as a carrier gas. When H-2 was used as a carrier gas, an incubation period was found (about 12 min at 0.2 Pa), during which Ge nuclei were formed on Si. After the incubation period layer growth of Ge film began. In the case where Ar was used as a carrier gas, the incubation period was drastically reduced without any apparent change in the layer growth r ate, The nucleus size was larger and the nucleus density was lower in the case of H-2 as carrier gas. These growth characteristics are belie ved to be caused by the suppression of adsorption and/or decomposition of GeH4 on the I-I-terminated Si surface in the case of H-2.