ABSTRACT
In this paper, we describe the application of photoreflectance (PR) to obtain the surface electric field and carrier concentration in moderately and heavily doped nanoscale epilayers of GaAs in a contactless manner. The technique exploits the PR line width of the E 1 response (~2.9eV). This is described by the empirical broadening parameter Γ1, which we find increases linearly with the logarithm of the carrier concentration and the surface electric field beyond ≈ 1017 cm −3. The slope of the linear relation for n-GaAs is nearly twice of that of p-GaAs. We explain the observed effect by the Schottky relation and Fermi level pinning and show that this effect is a function of the field intensity near the surface. We also show that the PR line shape at E 1 is applicable in determining the field intensity and the carrier concentration of a nanometric GaAs layer in the vicinity of the surface.
