Electrical Properties of Epitaxial Ge Films Deposited on (111) CaF2 Substrates

Abstract

The temperature dependence of the Hall constant, resistivity, and Hall mobility was measured for Ge films deposited on polished (111) CaF2 substrates at substrate temperatures of 200°–700°C, deposition rates of 100–15 000 Å/min, and for film thicknesses between 800 and 170 000 Å. For formation conditions which improved film structures, electrical properties likewise improved. For single-crystal films the Hall constant and Hall mobility increased as the defect density decreased with increasing deposition temperature and decreasing deposition rate. Similarly, for films thicker than 4000 Å, as the density of defects intersecting the surface decreased with increasing thickness, the Hall constant and mobility increased. Hole-carrier concentrations of 1016–1018 per cm3 and room-temperature Hall mobilities of 100–1100 cm2/V·sec were observed. The results indicate that defects are the source of acceptors and contribute significantly to scattering.