The Interaction between Oxygen and Boron in Liquid Germanium

Abstract

Germanium crystals containing oxygen and boron concentrations up to approximately 6×1017 atoms/cc have been grown by the Czochralski method. Electrical conductivity, Hall voltage, and infrared absorption measurements have been made. It is shown that an interaction takes place between boron and oxygen in a germanium melt. In the subsequently grown crystal the oxidized boron is incorporated in a neutral state that neither provides nor measurably scatters charge carriers. The distribution coefficient of the boron in the oxidized state was found to be much less than K = 7, the value that is applicable to elemental boron at the growth rate used. The reaction is reversible in the melt. On dissociation of the boron-oxygen compound, the initial rate of dissociation and reappearance of the boron as a p-type dope depended on the rate of removal of the oxygen from the melt. Boron-doped crystals of essentially constant resistivity were grown from melts containing boron and oxygen. In ``as-grown'' oxygen-doped crystals less than 0.03% of the oxygen present gave rise to donor levels when α, the optical absorption coefficient at 11.7 μ, was 4 cm−1, the error involved in the measurement of the oxygen concentration by the absorption at 11.7 μ became significant.