Ge films grown on Si substrates by molecular-beam epitaxy below 450 °C

Abstract

Ge thin films are grown on Si͑001͒ substrates by molecular-beam epitaxy at 370°C. The low-temperature epitaxial growth is compatible with the back-end thermal budget of current generation complementary metal-oxide-semiconductor technology, which is restricted to less than 450°C. Reflection high-energy electron diffraction shows that single-crystal Ge thin films with smooth surfaces could be achieved below 450°C. Double-axis x-ray /2 scans also show that the epitaxial Ge films are almost fully strain-relaxed. As expected, cross-sectional transmission electron microscopy shows a network of dislocations at the interface. Hydrogen and oxide desorption techniques are proved to be necessary for improving the quality of the Ge films, which is reflected in improved minority carrier diffusion lengths and exceptionally low leakage currents.

Germanium Band Gap Engineering Induced by Tensile Strain for Si-Based Optoelectronic Applications

“…We note that to obtain the value of the in-plane tensile strain ε // , we first determine the out-of-plane strain ε ⊥ from the θ-2θ XRD curves and then deduce the value of ε // using the following relationship: ε // (ε /// + ε ⊥ ) = c 11 /(c 11 + 2c 12 ) with c 11 = 12.85 x 10 10 Pa and c 12 = 4.83 x 10 10 Pa for pure Ge [19]. The highest value of the in-plane tensile strain ε // obtained in the growth temperature range of 700-770˚C is 0.24 %, which is in good agreement with previous results reported using CVD in which the highest tensile strain was in the range of 0.22 -0.25 % [1,[13][14][15]20] at similar growth temperatures. Shown in Fig.…”

Crystalline growth of germanium thin films on single crystal silicon substrates by solid phase crystallization

“…The c-Ge films can be grown by epitaxial growth on single crystal silicon (c-Si) substrates which are used as a crystalline seed. The epitaxial growth is usually done by ultra-high vacuum chemical vapor deposition (UHV-CVD) or molecular beam epitaxy (MBE) [5,6], but these methods are not appropriate to make large area devices such as solar cells and so on. On the other hand, solid phase crystallization (SPC) from amorphous Ge (a-Ge) possibly gives us a large size and low-cost process [7].…”

Specific features of formation and propagation of 60° and 90° misfit dislocations in GexSi1−x/Si films with x>0.4

“…The amount of defects in such heterostructures was reduced by growing Ge or close to Ge layers of GeSi at low temperatures with subsequent cycles of annealing [1,2]. Surface-active impurities (surfactants) were used to make the growing film surface planar [3][4][5][6][7].…”