Si/InP(110) heterojunction.

Abstract

An investigation of the morphology and energy levels at the Si/InP(110) interface for Si overlayers up to 12 monolayers thick was performed with use of photoemission, Auger-electron spectroscopy, and low-energy electron diffraction. Changes in the heterojunction morphology were observed by growing the interface at two temperatures, 20 and 280?deC. The intensity of the substrate core levels for both growth temperatures indicates laminar growth of the Si overlayer with some In and P included with the overlayer. At 280?deC growth temperatures, the substrate atoms are present in the overlayer in larger amounts. Examination of the chemical shifts in the In 4d core level which are resolved for the room-temperature Si/InP(110) interface shows two distinct contributions and indicates either surface segregation or intermixing of In. At higher growth temperatures, the In 4d peak is broader and may be due both to intermixing and to surface segregation. The P and Si ${L}_{2}$,3VV signals indicate no bonding changes involving those species; however, the P 2p peak shifts in a way inconsistent with what is believed to be the band bending, and thus must be involved in a different chemical environment. Band-bending changes cease at low coverages such that the conduction-band minimum of InP is 0.4 eV from the Fermi level at the interface. The rapid stabilization is consistent with the defect model. The band-bending position is determined from the In 4d peak at low coverages and is difficult to determine at higher coverages since both the In 4d and P 2p peaks have chemically shifted components. Higher-temperature growth of the overlayer mostly changes the degree of intermixing of overlayer and substrate atoms. It does not affect the electrostatic dipole at the interface, and affects the heterojunction discontinuity only slightly. The valence-band discontinuity is 0.56 and 0.46\ifmmode\pm\else\textpm\fi{}0.1 eV for the 20 and 280?deC growths, respectively. These values are in agreement with those in the literature.