Growth of high quality epitaxial Ge films on (100)Si by sputter deposition

Expitaxial Ge films ∼1.5 μm thick, were grown on (100) Si substrates at relatively low temperatures, 470°C, by rf sputter deposition. Low-energy ion bombardment of the substrate and growing film during deposition provided compositional grading of the lattice mismatched interface. X-ray diffraction and electron channeling spectra indicated that the films were single crystals while Hall measurements showed them to be p type with p(300 K)≃1×1017 cm−3 and corresponding carrier mobilities, 1280 cm2/Vs, comparable to the best bulk crystals. The thickness of the compositionally graded junction was found by Auger electron spectroscopy depth profiling to be ∼200 nm. C-V measurements indicated that over this region the net acceptor concentration increased from 4×1014 cm−3 near the substrate surface to the bulk film value of 1×1017 cm−3. Large area p-n diodes exhibited reverse breakdown voltages of ⩾10 V.