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

Expitaxial Ge films approx.1.5 μm thick, were grown on (100) Si substrates at relatively low temperatures, 4700C, 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)approx. =1 x 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 approx.200 nm. C-V measurements indicated that over this region the net acceptor concentration increased from 4 x 1014 cm-3 near the substrate surface to the bulk film value of 1 x 1017 cm-3. Large area p-n diodes exhibited reverse breakdown voltages of > or =10 V