Morphology and Schottky barrier formation at metal/III-V-semiconductor interfaces.

摘要

Measuring and understanding the potential barrier development at metal-semiconductor interfaces is of both practical and fundamental interest. This dissertation examines the development of this potential barrier (the band bending) as a function of metal coverage for a variety of overlayer growth modes. Three issues were of specific interest: (1) characterizing the various growth modes as a function of parameters such as interfacial reactivity and substrate temperature, (2) establishing the influence of the growth mode on photoemission spectroscopy (PES) measurements of band bending, and (3) determining the influence of the overlayer morphology on the band bending itself.;A representative range of overlayer morphologies was observed in our photoemission studies of room-temperature-grown metal/GaP interfaces: reactive overlayers (Al, Au, Cu, Ni, Pd, Al), clustering overlayers (In, Ga, Ag), and ordered, covalently-bonded overlayers (Sn, Sb, Bi). These growth modes were characterized by studying changes of the substrate and overlayer core level spectra as a function of coverage. The bonding of the ordered, covalent systems is of particular interest, providing information pertinent to epitaxy, bond saturation, and surface energy minimization. We have studied the detailed bonding of the 1 ML Sb/GaP (110) interface using the Surface Extended X-ray Absorption Fine Structure and X-ray Standing Waves techniques.;The band bending for certain "model" overlayer morphologies has been characterized. The Bi/Inp (110) system is determined in our PES study to be an ordered, covalently-bonded interface. The band bending established from this PES data suggests that the submonolayer interfacial states are largely attributed to the peripheries of two-dimensional Bi patches. Other unreactive overlayers such as Ag, In, and Ga form clusters on III-V semiconductor surfaces, and these clusters exhibit metallic characteristics from the lowest detectable coverages. The influence of metal clusters on the underlying semiconductor surface potential was quantified using a three-dimensional Poisson solver. We conclude from these calculations that the submonolayer band bending measured by PES from such systems is beyond the influence of the clusters and must be attributed to surface charge states between the clusters.