STRUCTURE AND CHEMICAL BONDING AT THE INTERFACES GAAS/SI AND GAAS/GE

Bevelled samples of GaAs layer grown by metal-organic vapour phase epitaxy on Si(100) and on Ge(100) was shaped to allow microRaman spectroscopic studies at different areas as small as 1 μm square, from the substrate, to the interface and to the outer surface of the GaAs deposit. For GaAs on germanium, at the interface, germanium is found to become locally disordered, as well as GaAs. New bands appear at 286 and 280 cm- which can be assigned to new chemical bonds AsGe and GaGe between the deposit and the substrate, in agreement with the amphoteris character of germanium. For GaAs on silicon, the same modification of the GaAs lattice is attested by a strong enhancement of the TO band at 269 cm-1, which was initially forbidden. The broadening of the silicon band and the lowering of the frequency of its maximum is also proof of local disordering of the silicon network. Finally, only one new band appears at 391 cm-1 which can be assigned to new chemical bond AsSi.No GaSi bond was observed as in the case of GaAs/Si, as silicon diffuses into GaAs as an n-type dopant. © 1990.