Epitaxial growth and band bending ofn- andp-type Ge on GaAs(001)

Publisher Website
Google Scholar
Abstract
We have combined high-resolution x-ray photoelectron spectroscopy, low-energy electron diffraction, and x-ray photoelectron diffraction to examine the interface structure and band-bending characteristics of n- and p-type Ge epilayers grown on semi-insulating GaAs(001). The first monolayer of Ge intermixes with atoms in the near-surface region to yield a complex structure. Subsequent Ge monolayers grow epitaxially but exhibit surface roughness in the form of local variation in layer thickness of the order of 2–3 monolayers (3–4 Å), in agreement with previous reflection high-energy electron diffraction measurements obtained during continuous overlayer growth. The growth of undoped (which is actually p type) and As-doped Ge overlayers results in Schottky-barrier-height changes of +0.05 and -0.35 eV, respectively, relative to the clean-surface value of 0.83±0.05 eV. Furthermore, the barrier height correlates directly with dopant level in the Ge epilayer. In contrast, the valence band offset is independent of dopant level in the Ge film and maintains a constant value of 0.60±0.05 eV. With the exception of the barrier height of the starting surface, these results are the same as those obtained on n-type substrates, further supporting the conclusion that barrier-height formation and band-offset development occur independently.