The growth and electrical properties of silicon on GaAs(110) studied by scanning tunneling microscopy and scanning tunneling spectroscopy

A scanning tunneling microscope (STM) has been used to study the structural formation of silicon overlayers deposited at room temperature on GaAs(110). In addition spectroscopic measurements were obtained simultaneously to reveal electrical properties associated with the interface and overlayer formation. The Si coverage varied in thickness from submonolayer growth up to ∼16 monolayers. The height variations of the STM images indicate that silicon islands did not exceed ∼3 Å at either submonolayer growth or thicker coverages. The lack of atomic resolution of the adsorbed silicon suggests that the silicon overlayers are amorphous in nature, confirming soft x-ray photoelectron spectroscopy (SXPS) measurements. The scanning tunneling spectroscopy measurements clearly indicate a Fermi shift of 0.8 eV when silicon was deposited on the clean cleaved surface of p⁺ GaAs(110). This shift is also observed on regions of the substrate which remained exposed after the silicon deposition. The Fermi shifts and resultant band bending are attributed to the formation of the Si–GaAs heterojunction and correlation with earlier SXPS measurements prove favorable. The possibilities of measuring the band offsets are also considered. © 1999 American Institute of Physics.