Catalytic and chemical reaction rates of hydrogen atoms with germanium

Abstract

Abstract : The chemical and catalytic reactions between hydrogen atoms and the semiconductor germanium are investigated in order to examine the dependence of these reactions on the bulk electronic properties of the solid. Two reactions with gaseous hydrogen atoms were explored; viz., the catalytic recombination of hydrogen atoms on the semiconductor surface and the chemical reaction in which a volatile germanium hydride is produced. The recombination coefficient for hydrogen atoms on germanium was determined for crystals of different doping levels (both n-type and p-type). At 90 C, the recombination coefficient was found to be 0.25 = 0.06, and was essentially independent of the atom density in the gas and the doping level. The recombination coefficient could be correlated with the Debye temperature of the solid as found previously for metals. As the germanium temperature was increased from 90 C to 170 C, the recombination coefficient increased about 50%. The hydride formation reaction rate was found to be first-order with respect to the hydrogen atom density in the gas with a rate constant at 25 C of 1.4 = 0.2 cm/sec, independent of doping level. It is concluded that the bulk electronic properties of germanium, and probably also of silicon, do not appreciably affect either the catalytic properties for hydrogen atom recombination or the chemical properties for volatile hydride formation. (Author)