Jma. Gilman et A. Hamnett, ELECTROREFLECTANCE MODELING OF LOW-FIELD DIELECTRIC CONTRIBUTIONS REQUIRING A BOLTZMANN MODEL OF CARRIER DENSITY, Semiconductor science and technology, 8(7), 1993, pp. 1475-1478
Electroreflectance spectroscopy is a useful diagnostic tool for potent
ial and field distribution in semiconductors, and spectra from experim
ents performed on samples taken from highly doped (near-degenerate) wa
fers of III-V materials have been compared with theory. Satisfactory m
odelling has been achieved using recent advances in the understanding
of the Moss-Burstein (band-filling) effect, and the accurate modelling
of bandgap narrowing and other heavy doping properties is also demons
trated. The Moss-Burstein effect makes its principal contribution to t
he dielectric function in the low-field region, as does that of excito
nic absorption, and both effects are shown to require special computat
ional considerations with respect to the electric field profile. When
a Boltzmann carrier concentration (rather than a Schottky depletion) m
odel is used, the calculated result for the Moss-Burstein effect rapid
ly converges to the correct lineshape. The use of the Schottky depleti
on model is shown to result in much slower convergence to a signal of
much smaller magnitude, and a simple excitonic calculation shows the s
ame tendencies, clearly demonstrating the importance of a correct fiel
d profile model.