Evidence for germanium phosphide dots on Ge(001)

The Ar ion sputtered and annealed (001) surface of a 0.2 Ohm cm resistivity P doped Ge crystal has been investigated in ultrahigh vacuum using scannin g tunneling microscopy (STM), STM light emission, x-ray photoelectron spect roscopy, Auger electron spectroscopy, and low energy electron diffraction. The preparation procedure results in an areal concentration of 1.0+/-0.5 at % of P, approximate to 70% of which is in compound form and the remainder in elemental form. The P atoms diffuse to the surface and subsurface region s during annealing to 880 K. The evidence is that the compound is most prob ably metallic GeP3 which forms nm scale dots on the surface, while the elem ental P is most probably in the subsurface region. The existence of the met allic phase is consistent with the presence of large (similar to 10-100 kba r) compressive heteroepitaxial stress induced in the dots by the substrate. (C) 1999 American Vacuum Society. [S0734-2101(99)01403-7].