Passivation of the Ge/InP(110) interface by As interlayers: Interface reactions and band offsets

The formation of the Ge/InP(110) interface at room temperature and the infl uence of an additional arsenic interlayer on the interface chemistry, the f ilm growth, and the electronic properties of this heterostructure have been investigated using core and valence level photoemission and low-energy ele ctron diffraction. We have shown that an As interlayer at the Ge/InP(110) i nterface can completely suppress the interface reaction of the Ge with the substrate at room temperature, including partial In-Ce exchange and In segr egation. The electronic situation at the interface is characterized by an a nomalous evolution of the surface Fermi level with Ge coverage on InP(110) and a high valence band offset of Delta E-v = 1.01+/-0.07eV, which is reduc ed to Delta E-v = 0.78 +/-0.07 eV for Ge/As/InP(110). We may attribute the differences of the measured valence band offsets to a reaction-induced inte rface doping of the InP at the real Ge/InP(110) interface, which introduces an interface dipole layer. A calculation of this interface dipole contribu tion (0.38 eV) using the model of interface induced gap states gives a fair estimate for the experimentally observed difference of the valence band of fsets. (C) 2000 American Vacuum Society. [S0734-211X(00)05304-X].